Now the main editor in flickr, picnik has the simplicity that you need for quickly resizing or cropping your pics for online use. Image quaility in resizing is much better than Splashup
ExtremeTech.com
Picnik isn't about trying to be an online Photoshop, but rather is intended as a way to give digital shutterbugs a convenient way to fix up their snapshots. Its competition in the installed software world is Picasa rather than Photoshop. But don't think it's a simple rotate and red-eye correcting app: Picnik offers plenty of impressive capabilities.
LifeHacker.com:
There's quite a bit to Picnik, actually: you can do the basic resizes and tweaks that most other free image editors we've talked about here at Lifehacker can manage; however, Picnik also comes with some nifty special effects, and can be used with a whole plethora of community photo sharing sites, i.e., Flickr, Imageshack, Photobucket, etc. It's not as powerful as Photoshop, naturally, but for a browser-based image editor, Picnik does a fine job.