Was just participating in my daily lunchtime random surfing and stumbled upon Velesoft's page. I've actually seen it before, but thought I'd mention it now because... well, I just am. I guess after getting my plus3e set up I'm in modding-mode. Over on Velesoft's page you can find details of a load of mods for the ZX, Sam, Timex, and Sprinter. Some of interest at the moment include Turbo-Sound (dual AY chips), DivIDE Memory Enhancements, and a "Convert your +2 into a Pentagon 512" board. That sounds like an interesting one... wonder if it fixes the memory contention? Of course I can't tell as the site is mostly in Czech. I don't think my phrasebook includes sections about soldering.
Also of interest to the gamers out there (of which I'm one) there's a bunch of software modded to use the Kempston Mouse interface. I've played Flying Shark with a mouse and it's rather nice (tho' perhaps too easy?). But Carrier Command should be fantastic - now I just need the bloody mouse.