It will vary depending on your camera and the settings. At full resolution I'd think you should get about 200-300 in full-res/uncompressed format. Lots of cameras have adjustable settings; my 2mp Canon PowerShot s200 has 3 resolutions; 1600x1200, 1024x768, and 648x480. In addition I have 3 choices for compression (more compression = more grainy but smaller size). So there are a whole bunch of possible answers.
For my camera, a 1600x1200 uncompressed image is about 1MB, so you could get 250 or so on your card. Drop the resolution down or increase compression and those numbers will go up.
Hope this helps!
-Pete