FatBits magnifies an area of the screen centered around the mouse pointer and paints the giant pixels into a small, tastefully decorated window. This can be indispensable when you want to see something right down to the last pixel. Once the text has been magnified (up to 20x), Fatbits can also smooth it, and change the colours used. The website contains an online User Manual.
FatBits was originally designed for graphic artists or people designing user interfaces, but it may be relevant to some people with visual impairments.