Adobe	Makers of Photoshop.
Corel	Makers of Paint Shop Pro.
Paint.NET	A free image editor which started out as a replacement for Microsoft Paint and now does photo editing.
Tesco	Yes, one of the UK's largest grocery chains is selling a software package called "PhotoRestyle" for about £10.00.
Gimp	Alternatively, GIMP is completely free - just download it.
VueScan	Independent Scanner driver software supporting many different scanners.
Bibble	Independent RAW conversion software.
Photomatix	Use multiple exposures to increase the dynamic range of your photographs.
Focus Fixer	Claims to refocus out of focus pictures!!!
Focus Magic	Yet another outfit which claims to be able to refocus out of focus pictures! This one is cheaper.

Extensions to Photoshop

Earthbound Light	Adds the Curves feature of "Full" Photoshop to Photoshop Elements versions 1, 2 and 3.
SmartCurve	Adds the an extended Curves feature to all versions of Photoshop (Elements and CSx). The web site says that it also works with Photoline, PaintShopPro and Irfanview.
Layer Masks	Adds the Layer Masks feature of "Full" Photoshop to versions 6, 7 and 8 of Photoshop Elements.
Genuine Fractals	Interpolates small files to create large files.