Gmail: Tons of space, quick, clean interface, labels, non-intrusive ads. It's a winner 🙂
As for fastmail.fm; the free (Guest) version doesn't offer a lot of diskspace, and will expire after 45 days without activity (so remember to log in), but it does have IMAP support, if you need that. A one-time fee (upgrading to Member) will increase the diskspace slightly, plus remove the tagline from the e-mail, and the account will never expire. You can also increase the diskspace for a one-time fee.
Have an Enchanted account there, which I'm very happy with.
But, honestly, you can't really go wrong with gmail.