If you are spending less than $100, I'd recommend the following:
http://www.monoprice.com/products/pr...seq=1&format=2
These are currently on sale too...probably get them for around $20 shipped. The reviews, however, are fantastic. The quality far exceeds the price.
http://www.meelec.com/
The reviews on this brand of earphones are similarily fantastic. The quality far exceeds the price.
The trick you're going to have with the $100 budget is that it's a price range that many companies offer their lower quality earphones at, and you end up paying largely for branding. IMO you should go with my suggestions or be prepared to spend in the $200-$250 range for audiophile style earphones.