I think the Canon EOS Rebel XSi EF-S is probably the best bang for the buck when buying a digital camera in the cannon series. It utilizes the same processor as the pricier 40D and 5D. The casing and some of the motorized parts are where they skimmed to make this camera more cost efficient.
The most important thing to look for in a digital camera is the Processor and the Lens. With the Canon you have a large verity of top dollar lenses to choose from. When choosing a lens, try to lean towards fast glass that contains aspherical glass elements. (The lower the F stop or aperture rating the better the lens) Out of the box lenses are sufficient, but rarely capture the images you desire.
When it comes to point and shoot cameras the same rules apply, Possessor and Glass. The lens on these cameras are the most important attribute to the image capture. It should have a high level of Optical Zoom 10x to 12x. Keep in mind that Digital zoom equates to image noise and motion blur. The next most important thing is the cameras automatic exposure metering. I prefer Olympus cameras when it comes to the point and shoot cameras in this category. They have an excellent exposure rating. For computer use it really doesn't mater what level of mega pixels the camera has, anything from 2.0 and above will be sufficient for any and all posts. For my computer use I have an Olympus C-700 that I bought in 2002. They can be bought for a hundred bucks or less on ebay. It's 10x optical and contains 3 aspherical glass elements. The cards are smart media and a 128 mg card can be bought for about 10 dollars or less off ebay. A bang for the buck no worries no hassle little camera for computer use.
If you want to step up a little from the Olympus, the Fugi FinePix S700 would be the best bang for the buck, go to, point and shoot camera in my opinion. After that I would put my money on the Canon.
Even with the finest camera in the world, lighting plays the most important factor in capturing a solid image. Diffused sunlight or multiple points of soft light will yield the best results. I hope this helps.