Steve Fryatt is a well-known face in the RISC OS world and a regular fixture at RISC OS shows where his stand always has lots of interesting software.
His website hosts lots of free software including the free home accounts software
CashBook. This has recently reached release 1.41
There are utilities like
Locate,
PrintPDF and
PS2Paper, lots of
games.
If you are looking to write your own software, there are
Build Tools and a guide to
Wimp Programming In C Steve also has some interesting pages on his website on his non-RISC OS activities.
Steve Fryatt's website 
