Hi! For those of you interested in writing music for the Atari 8-Bit computers a fellow by the name of candle has made (and is making) some relevant products.
A FPGA replacement for the video chip in the Atari. Has added graphic modes that look quite nice! Also provides high quality video outputs.
A dual POKEY upgrade as well as the Covox sampler (MOD's) in one. Requires a small IO Board that has a ps/2 adapter as well and a SIO2PC interface.
A 1MB (!) memory upgrade for the Atari. Has an alternate DOS SpartaDosX built in as well as a real time clock that SDX uses. A very handy combination of different products already available, not to mention how easy the install is.
A 2.5" hard drive interface as well as CF and SD card interfaces. Won't have any problems storing data with this. 
Another sound expansion. The features seem to be in the air a little bit, but it looks to have full emulation of the Gravis Ultrasound PC audio card and a SID. The best part is that the author of NeoTracker is in on it and will be/is writing a tracker for it. This is all emulated in FPGA of course.
Exciting prospects! Check the links for more detailed info.
I also feel I should mention this. A nice standard stereo POKEY upgrade which is notable for its small size, and the fact that it has a preamp and lowpass filtering (bass boost) built in. Also the GTIA click is routed through as well which is dandy as 1-bit can join in on the fun too!