Even though the 20th Anniversary Macintosh is simply outstanding in its own right, it never hurts to improve on a good thing.  Here is a modest list of accessories to help you get more out of your TAM computing experience...

Memory (you must use 5 volt 64-bit 168 pin 60 nanosecond EDO dimms with a 1k or 2k refresh)

Resources for DIMMs
The Chip Merchant
Mac Gurus.
TechWorks
MacConnection
MacMall

Keyboards
Apple Design Keyboard, black (P/N 922-2327)
TechStyle Keyboards (enclosures made of exotic woods!)

Mice
Apple Desktop Bus II Mouse (P/N 922-2328)
Costar Stingray (yes, it comes in black) - available from MacConnection
TechStyle Mice (enclosures made of exotic woods!)

Modems
ComSlot II 56k modem kit (P/N652-0038)

Ethernet Cards
ComSlot II 10Base-T Ethernet (P/N 661-1171)
Sonic 10Base-T Twisted Pair (P/N 01-SSC-0425)