Image editors (simple, online and free)

Web Resizer is the only one of these three that I have used myself on several occasions. It is meant for just a few simple resizing and/or cropping tasks, but it's very easy to use and I have never experienced any problems using it.

When looking for alternatives —meaning: also free, online and simple— I found two others, but I must say that I haven't really used them:

• Pic resize looks similar in capabilities as Web Resizer, with some more "special effects", but in the few tests I did it also seemed a bit slower.
• Splashup has the most features of these three.