I haven't seen mailboxforwarding.com mentioned very much in this thread, so I thought I'd give my review of it. I've been using it since I moved to Germany two years ago without a single hiccup. Mail is scanned within 24 hours.

The only caveat is watch out for the mailstorage fees, shred the mail you don't want and ship the others. I had one month with a bill of $60 (with ~9 months of mail stored).