Programming quotes at cat-v.org.
Compiler explorer is a fun and useful interactive online compiler for many programming languages including C.
BBC Micro Bot is a Twitter 'bot' that runs tweets on an emulated BBC Microcomputer, thereby providing an outlet for creative coding within a strict character limit.
Martin has infrequently-updated accounts at both Twitter (NSFW) and deviantART.
Christopher has accounts at both Twitter and Medium.
Quantum Software used to have a very nice selection of picturesque desktop backdrops for download, which have now thankfully been preserved.
Jared Tarbell's Gallery of Computation showcases amazing computer-generated artwork, some of which has a startling resemblance to natural forms.
The Brick Bible is a fascinating recreation of many Bible stories using LEGO building blocks. Gain invaluable knowledge such as 'When to Stone Your Whole Family'!
The Thunderbirds Drinking Game might enliven an evening if you are fond of this classic 1960's television series.
Tom Hughes's WimpMon is an essential tool for any RISC OS programmer.
Jan-Jaap van der Geer's DirSync is another essential tool — not only for programmers but for any RISC OS user. It shows the differences between two directory trees, side-by-side, and allows them to be resolved interactively.
I'm a late convert to Director (which is why my sister wrote Switch), but nowadays I would not willingly use RISC OS without it. It has far more features than I will ever understand or need, but the ability to browse the directory tree instantly by clicking on any window title is a killer feature for me. This puts RISC OS ahead of every other desktop I've used. Of course, it also lists all windows on the desktop (like Switch).
Funnies (a.k.a. Your Slice of Geek Culture) - collected from various sources by Richard Murray.
The Flying Pig's Decide program is an imaginative desktop silly that helps you make decisions.
Zarquon's Manifesto is an amusing rant on various topics including the Microsoft monopoly, computer illiteracy, dominance of style over content, bad movies and the music industry.
Most of Christopher's other programming efforts are related somehow to the Acorn RISC OS game Star Fighter 3000.
Christopher's entry on the Doom Wiki.