http://mail.yahoo.com is the link to sign up for yahoo. It's probably the best free provider left out there. If you don't have to have it free, try getting your own domain name. . . you can usually pay 15-20 bucks for a year and get 25 megabytes of storage space to divide up as you like, which is usually adequate, especially if you couple it with an email program like outlook express.
A note: Yahoo mail does NOT work with outlook express- you have to read mail from their website, and you can only save, I believe, 3 megabytes for each account. If you receive a lot of big emails, that'll go fast.