Currently between games for either work or pleasure, I idly browse for brief, cost-free delights to tide me over until some new pixel shaded murder simulator sets up shop on my hard drive. I find these, amongst others.
Hell (pictured) is a horizontal shmup in the vein of Gradius, and impressively was made in just four days, including music. Your ship's auto-firing throughout, which may prevent the RSI blues, but a similarly near-constant stream of deathrays from your enemies keeps up the challenge.
Jet Set Willy Online - The online bit I sadly can't attest to yet, as I can only find one server, which I can't seem to connect to even after extensive firewall faffery. You may have more luck than I, in which case please share your impressions below. It's a remake of the beloved and, even to this day, reliably weird Spectrum platformer that now supports up to 16 players a-collectin' and a-jumpin' at once, as well as offering up a splendily-realised singleplayer mode containing 255 rooms. Taking it online is a fine idea, though my mind struggles a bit to imagine how 16 competing Willies actually works in practice. Oh - tread carefully around its website, as the barrage of penis gags rapidly becomes vexatious.
Worthy casual game Planetcruncher sadly does not involve the crunching of actual planets. It does involve ensaring them with a magic space-rope, causing them to explode into either sparkly gemstones or flying black holes, which is almost as fun. I am entirely unsure as to the reason for such intergalactic lassoing, however: perhaps an RPS reader would like to think up a ludicrously elaborate backstory for it.
Finally, the ongoing quest to bring graphics to Dwarf Fortress continues. 3Dwarf isn't playable as such, but it does allow you to admire your mighty citadel from within a proper 3D engine blessed with a repositionable camera. Crysis it ain't, but it certainly introduces a grand sense of scale to the game also known as Chapter II of Slaves To Armok: God of Blood, and a chance to seriously visualise your creations with something other than your feeble imagination. Seems like the DF community is going nuts for it, so perhaps it can be considered a glimpse of things to come. There are various intruiging ruminations as to whether it could ever realistically be expanded into a fully playable 3D mod downthread in the linked page, and the chance to boggle incredulously at an enormous statue that a player named Kennel painstakingly constructed over 10 long months. (In-game months, mind.)