If you're NEVER EVER EVER going to use any 3D whatsover, then any old ATi or Matrox card in the 8mb or higher range will do just fine These can be found cheap ($30 or less new, or free if you know folks upgrading).
If you're using alot of photoshop or doing any graphics or desktop publishing regularly, then I'd get a Matrox g450 or any of the 32mb or higher Radeon's.
Hell, I've got some old 2mb S3's on alot of NT workstations that still look great for 2D desktop apps.