I really thought this webservice was already discussed but a search didn't turn anything up:
Picnik lets you edit all your photos online, from one easy place. It's the most amazing webapp i've ever tried: it does everything picasa does (well.. not the organising functions) right in your browser.Picnik -- online 'picasa'-like webapp
Crop, resize, autofix, redeye,rotate, exposure etc etc it's all here and it works like a charm! Even filters like distort and blur. It can crop to any dimension, as well as several webservices (last.fm, myspace) avatar sizes.
Load and save straight to flickr. Yep. Definately worth a look.