Well, the Risc CPU, ugly as it has become, is still alive in PDAs and the such. The OS software itself is the same as it ever was. Apps are scarce, but at least the hardware guys are still active (a bit), and some drivers still get developed. But all that is on the RiscPC side of things, but since it uses the 'Risc OS', as Archimedes did, those OSes are still commercial.
I would hardly call the Archimedes alive, and RiscPCs are used mostly by enthusiasts and some remain in schools in the UK I guess, running the same old programs. But though it's great to see hardware still being developed, it's a bit of a letdown on the software front.
I've emulated a bunch of games on the good old Archie (as well as run them on my Archimedes A3000) and few are as neat as all the Amiga games, it never took off as a games platform. In fact, most of them are terrible, with Elite and Zarch being the shining stars. (And Zarch really is fantastic on the A3000 - on faster machines it's unplayable unless you somehow degrade the speed.)
I have an A3000 because that was when the CPU still was beautiful, and it was another of the fantastic computers Acorn made, a great landmark when it came (just after the Amiga 1000!). Their BASIC really is the most intellectually appealing version of all BASICs ever written, with Acorn Atom BASIC as close second.
Certainly, the Archie/RiscPC scene is tiny, and it doesn't contain the great people of the Amiga scene collecting, hosting, researching, and developing the software that came out for it. And certainly not such busy forums as ours.
Redsquirrel is the best bet for emulating I think, if you want to do it for free. It does have limitations, though. But that's what I use, and it's worked well enough for me doing a small 'sprite snake' demo in assembler