http://shadowrun.chinagreenelvis.com is now an HTML quick reference site for SR4.
I've been working on this mostly to aid my own playing (because the hardcopy sourcebooks and PDFs can be a bit cumbersome to navigate), but I thought I'd share it. It's a work in progress; at the moment it is far from complete. I'll be making updates periodically. When I feel I have something more or less finished, I'll zip the whole thing up into something downloadable for people who play where there isn't a wireless Matrix-- er, Internet connection available.
Almost all of the information is copied directly from the sourcebooks, so if Catalyst takes issue with copyright and bothers to contact me about it, I'll willingly take it down. However, I'd like to point out that the site is not meant to (nor could it) be a substitute for the sourcebooks; its merely a resource for players who already own or have access to them.
The main page is the Javascript diceroller that I use when playing. I play on a 1280x800 laptop, so I open this in a web browser on one half of the screen, and my fillable PDF character sheet on the other half. Until HeroLab releases their Shadowrun setup, I find this to be a pretty decent alternative.