If you'd like the power of Photoshop without the complexity or hefty price tag, then Splashup Light is worth a look.
Splashup Light is a slightly stripped-down (and free) version of Splashup and features many powerful tools for manipulating and annotating images. These include standard functions such as tools to correct saturation, brightness and contrast as well cropping, resizing and rotating. The overall look of the Splashup Light interface is cheap and cheerful and all the major functions are clearly visible in button along the left and right side so there's no searching menu bars to find what you're looking for.
Some of the more advanced features allow you to blur and sharpen images automatically, including a slider bar to change the intensity of the effects. You can also annotate images with speech bubbles and plain text very easily. You can't, however, illustrate images with Paint-style tools and SplashUp Light only works with JPG and PNG formats, which is rather limited.
Overall hthough, SplashUp Light is a hell of a lot easier than Photoshop and while not as sophisticated as the latter, produces some pretty impressive results.