I'm thinking of upgrading to a more fully-featured Digital Piano, and was wondering whether there is either a website or perhaps a listing here somewhere of all the types of features available on digital pianos, and an explanation of what each feature is/does. Or perhaps even a supplemental listing of features that are overrated and perhaps should even be avoided?

Features that I probably would want are 88 weighted keys; MIDI; recording capability; headphone jack; multiple inputs (mixer)....but I'm not sure of what else might be good to have.

FWIW, I presently use a Yamaha PSR-220. I find the non-full keyboard a bit limiting and I can hear the impact of the keys reaching the end of their travel even when I use headphones. (It's a bit annoying).

Any help finding a guide of features to look for would be greatly apprreciated! Thanks!

Have a look at pianobuyer.com
Their listing includes (in the appendix) a comprehensive list of digital pianos (and acoustic, too).

Thanks, Mac! Excellent resource there.