I've used onebox for several years now. It's pretty good, here's a rundown of pro's and con's
Pro's:
Access your email, faxes, voicemail from whereever there's a web connection or phone line
Check mail by phone
Has addressbook and calendar features
Local phone numbers for voicemail checking
Free Service
No ads
Mail filters & blocks available
Will forward mail
Con's
Only 3mb of free space - pay monthly fee for more
Extensions for faxes suck... difficult to get people to do it
No easy way to send faxes to people
No POP access to mail folders
I like this service better than hotmail and yahoo because I can play voicemail directly from it. This was really good when I was job hunting cause recruiters seem to like to call you over emailing you.