Depends on what you mean by fast. Certainly faster than snail mail if you have a decent upload speed. Mine tops out at about 40 KB/s on my cable.

GoDaddy.com has an OnlineFileFolder product which you could use. I think it's about $20 for 10 GB (or is it 20 GB?).

XDrive.com is another one. I think you get a discount if you have an AOL account.

FTP can be a pain because of dropped connections but some FTP Servers and Clients support reconnect.

Another decent service but not for this purpose is Carbonite.com which can keep an offsite backup of your documents (IIRC, it's about $40 a year).