I have used System 6 for over 20 years and have the following recommendations:
First, I recommend using System 6.0.8, as it's the latest version and is extremely stable. You can download it free of charge from Apple's website.
SYSTEM ADDONS (INITS/cdevs)
1. Get the TrueType INIT and the TrueType fonts. If you plan on printing to any non-PostScript printer and want decent-looking output, you'll want this. Apple has these on their website.
2. Bomb Shelter is a freeware INIT that forces the "continue" button to display on system error (bomb) dialog boxes. Since crashes are an inevitable part of computing, this is a must. It barely uses any RAM and is only a few K on disk.
3. If you don't have a physical programmer's switch, look for Programmer's Key, which enables a keyboard reset and interrupt command. You'll use the tilde key on a Plus since it doesn't have an ADB keyboard with a power key. I think Programmer's Key is free offhand (it may be shareware). I know Interrupt Button (a competing INIT) is shareware.
4. Backdrop is one of the coolest add ons for System 6. It allows you to use a MacPaint file of your choosing as the desktop pattern. Resize and dither a photo on a utility for a newer Mac, convert it to MacPaint format, and amaze your friends as you show off your favorite photograph on the desktop of your 20+ year old Mac! This one is also free.
5. SuperClock will place a menubar clock in the corner of your screen. It's another free utility and gives you yet another modern convenience we take for granted in our operating systems of today.
6. SCSI Tools is another great SCSI utility. It's freeware and helps to troubleshoot problems with SCSI chains.
7. If you have 4MB RAM and no hard drive, consider using RAMDisk+. This shareware utility will create a RAM disk and can be used to load the entire System into memory, freeing your floppy drive and allowing you to be rid of the startup disk. Very useful if you have only one floppy drive, but also has some use if you just want to use a RAM Disk.
8. Don't forget about MultiFinder! It's part of System 6 itself and adds multitasking to the standard System 6 environment.
9. While not an INIT or cdev, I should at least mention DiskDup+. It's shareware (from the same guy who wrote RAMDisk+) and is great for duplicating diskettes. Again, a great tool if you have only one floppy drive (far more efficient than using the Finder).
PROGRAMS
1. For word processing, I generally go with MacWrite II. This program is not free but does tend to show up on eBay (I think there's a copy on there right now, in fact). It provides just enough power to do the basic tasks required of most word processors, runs pretty fast, and includes a pretty good spell checker. I have written an entire novel using MacWrite II (on a Plus, in fact) and find it can handle quite a bit.
2. MacDraw II and MacPaint are pretty cool. Again, these aren't free; you'll have to check eBay for these. MacPaint is the standard Paint-type program while MacDraw is object-oriented (more like a really light CAD program; I've used it for everything from creating forms to making duplicatable student books to laying out floor plans for algebra and geometry lessons).
3. Print Shop (the original version, not Deluxe) is good to have around for both the creation of material (signs, banners, letterhead, and greeting cards) and its library of graphics. The bitmapped clip art is of high quality and is one of my favorite collections. It's easily exportable from the program so you can use it with other applications. This is another commercial program; check eBay periodically for this one.
4. Battle Chess and Shufflepuck Cafe are probably my favorite games for the Mac. Shufflepuck is an air hockey game while Battle Chess provides chess with animations whenever a piece is captured (they will actually engage in combat). Both are commercial games; Battle Chess shows up a lot more frequently than Shufflepuck does.
First, I recommend using System 6.0.8, as it's the latest version and is extremely stable. You can download it free of charge from Apple's website.
SYSTEM ADDONS (INITS/cdevs)
1. Get the TrueType INIT and the TrueType fonts. If you plan on printing to any non-PostScript printer and want decent-looking output, you'll want this. Apple has these on their website.
2. Bomb Shelter is a freeware INIT that forces the "continue" button to display on system error (bomb) dialog boxes. Since crashes are an inevitable part of computing, this is a must. It barely uses any RAM and is only a few K on disk.
3. If you don't have a physical programmer's switch, look for Programmer's Key, which enables a keyboard reset and interrupt command. You'll use the tilde key on a Plus since it doesn't have an ADB keyboard with a power key. I think Programmer's Key is free offhand (it may be shareware). I know Interrupt Button (a competing INIT) is shareware.
4. Backdrop is one of the coolest add ons for System 6. It allows you to use a MacPaint file of your choosing as the desktop pattern. Resize and dither a photo on a utility for a newer Mac, convert it to MacPaint format, and amaze your friends as you show off your favorite photograph on the desktop of your 20+ year old Mac! This one is also free.
5. SuperClock will place a menubar clock in the corner of your screen. It's another free utility and gives you yet another modern convenience we take for granted in our operating systems of today.
6. SCSI Tools is another great SCSI utility. It's freeware and helps to troubleshoot problems with SCSI chains.
7. If you have 4MB RAM and no hard drive, consider using RAMDisk+. This shareware utility will create a RAM disk and can be used to load the entire System into memory, freeing your floppy drive and allowing you to be rid of the startup disk. Very useful if you have only one floppy drive, but also has some use if you just want to use a RAM Disk.
8. Don't forget about MultiFinder! It's part of System 6 itself and adds multitasking to the standard System 6 environment.
9. While not an INIT or cdev, I should at least mention DiskDup+. It's shareware (from the same guy who wrote RAMDisk+) and is great for duplicating diskettes. Again, a great tool if you have only one floppy drive (far more efficient than using the Finder).
PROGRAMS
1. For word processing, I generally go with MacWrite II. This program is not free but does tend to show up on eBay (I think there's a copy on there right now, in fact). It provides just enough power to do the basic tasks required of most word processors, runs pretty fast, and includes a pretty good spell checker. I have written an entire novel using MacWrite II (on a Plus, in fact) and find it can handle quite a bit.
2. MacDraw II and MacPaint are pretty cool. Again, these aren't free; you'll have to check eBay for these. MacPaint is the standard Paint-type program while MacDraw is object-oriented (more like a really light CAD program; I've used it for everything from creating forms to making duplicatable student books to laying out floor plans for algebra and geometry lessons).
3. Print Shop (the original version, not Deluxe) is good to have around for both the creation of material (signs, banners, letterhead, and greeting cards) and its library of graphics. The bitmapped clip art is of high quality and is one of my favorite collections. It's easily exportable from the program so you can use it with other applications. This is another commercial program; check eBay periodically for this one.
4. Battle Chess and Shufflepuck Cafe are probably my favorite games for the Mac. Shufflepuck is an air hockey game while Battle Chess provides chess with animations whenever a piece is captured (they will actually engage in combat). Both are commercial games; Battle Chess shows up a lot more frequently than Shufflepuck does.