When I traveled abroad by in my college years, I had all my mail forwarded to my parents' house. They would do triage on it: throw away the junk mail, deposit checks, and call me if there was anything important-looking. They forwarded some stuff to me, and even faxed some important letters (I was doing a job search at the time) -- the faxes arrived at the local post office in Costa Rica, and I would take the bus over there to pick them up.
Times have changed, and we don't get much snail mail anymore, but we haven't quite eliminated the need to deal with dead-tree documents and such. Luckily there is a 21st-century solution to this problem, without having to burden relatives with dealing with a bunch of your mail while you're living abroad: internet mail-forwarding services.
Google turns up lots of these services; we've been using mailboxforwarding.com, and it's been working great. The company gives you a new address, and you tell the US postal service to forward your mail to it. They scan all incoming mail and send email when you get some, and they post the images of the envelopes to your account on their web page. You look at the envelope and then select (a) Shred the mail, (b) Open it and scan the contents, or (c) Forward the mail to a different address.
The service costs a reasonable monthly fee, plus a handling charge for each letter that you ask them to scan or forward. The main downside is the setup that the US Post Office requires, which involves filling out forms in triplicate and getting them notarized. It's definitely been worth it -- check it out if you plan to be away for more than a month or two.