My state (Arizona) send out empty voter forms via email, so it got to me quickly, and I had to vote about 20 days early to make sure it got back to the US in time. They also had electronic tracking to let me know that my vote was received.
All US embassies offer blank voting forms for federal elections, and if you are concerned about mail speed or the safety of your mail, you can send it through the diplomatic pouch at the embassy (just drop it off with the correct postage). If it is a concern for many volunteers in your country, the peace corps may collect your votes to send them through diplomatic pouch (ours did not).
Also, many states allow you to return your voter forms by email or fax, so check that out and make sure to register as an absentee voter before you leave the US. Finally, I believe the rule is that if you want a ballot mailed to you, you need to confirm your absentee status every january, either electronically or through the mail.