Martin has infrequently-updated accounts at both Twitter (slightly NSFW) and deviantART.
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 Testament 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.
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.