In winblows days i used quite a number. I found Ulead was good for
serious editing and Xnview (which can be used on Linux) for basic
editing.

In ubuntu i couldn't get on with either F-spot or eog and remove them.
I find gthumb is a nice app for basic editing and resizing pics and
gimp for more advanced tweaking and haven't wanted to use anything
else. I did try Picassa but have to say i found it rather bloated and
some unnecessary features.