Zoho Mail seems like a pretty cheap deal. $1.25/user/month 1yr commitment for their 10GB/user email + calendar + contacts support according to the website. It says it can do Exchange ActiveSync and IMAP for connecting. This is currently my target for migrating my few email accounts.
I'd love to hear arguments for another service that's cheaper than that for just a few accounts. I don't really want/need all the extra document collaboration tools other services provide and I definitely don't want yet another Google/Microsoft account.