For some time now I have been raving about Google's email "gmail" and have pretty much moved my entire office away from outlook/exchange. The reason was simply better synchronization when I am dealing with a pocket pc, which uses outlook, the laptop, and the multiple desktop scenarios. Gmail just made sense, especially since I can utilize the pop server and forward mail from my own domain. So which one should you get? You may want to see what other services you may already be using. Such as if you are a yahoo messenger person, then it would only make sense that you would have a yahoo email account. Same applies if you are an MSN Messenger person, odds are you probably have a hotmail account, whether it is active or not.
Michael Arrington of TechCrunch has done a comparison.