Google's Gmail can be free registered now here without invitation, so take a look and check it out. I use it for almost two years and for me its simply the best E-mail-Experience.
Why Gmail is different ? Read
plus the Comments.
Wikipedia has a deeper description of Gmail and compares it
Another advantage is, that you create with the E-mail-Account a free account at Google and may use all the other great inventions and services, like Blogger, Notebook, Reader +,+,+