Xara Xtreme
Windows: http://www.xara.com/products/xtreme/
Open Source Linux/OsX: http://www.xaraxtreme.org/

Pros:
+ cheap ($79USD d/l)
+ has the capablities of both raster (like Photoshop) & vector (Illustrator)
+ can import/export Photoshop/Illustrator files
+ can use Photoshop plugins/filters
+ easy to use if you know another graphics program
+ fast rendering speed, can even render effects real-time

Cons:
- not widely used
- open source version is not really released yet (view-only tech demo)

If you were thinking about buying PaintShopPro, or even upgrading it, skip PSP & go for Xara.  If you have Adobe suite alread, even Xara might help you render files faster.

Resources:
TalkGraphics forum
XaraOne.com