Here's a web app we use for all of our GURPS gaming sessions -- it's got a little bit of everything (everything we need, anyway), developed over years of us figuring out what utilities we needed as we played and what failsafes we needed. Features:
* There's an over-all game timer for capturing how long a game session is (and can be paused for dinner breaks etc.). The game timer even keeps going if the browser crashes or the power goes out and your computer dies.
* A page for "mini-timers" (mainly for luck usage) that key off the main timer, so if the game clock stops the character's luck won't regenerate inappropriately.
* A page for writing down game notes, which includes backups for in case you accidentally delete things or the power goes out or etc.
* A simple dice roller in case you're somewhere where there's no dice available (what a dreadful thought!).
* A page for saving worksheets of calculations (for instance, all the pluses and minuses for casting a specific spell).
It's all HTML5 and uses offline storage, so once you've viewed the app once it should be available even if you're offline. Timers, worksheets, notes, etc., are all saved to the local computer.
It's optimized for Safari, though should also run fine on Chrome or Firefox. Not tested on Opera, and all bets are off if you're using IE. Also, if you're using it on iOS and save it to the home screen, it will run in fullscreen mode.
http://www.buffalogalsnm.com/gamepad/
Enjoy!