Let’s say, you can’t or don’t want to afford a reflow oven, and you are doing things on low budget [and you know to read or translate a little German]. Then you might be interested in this page (http://www.heise.de/hardware-hacks/artikel/smd-loeten-in-der-pizzapfanne-1276166.html). They are approaching SMD (un)soldering in a home-made fashion. In an update to their first post (http://www.heise.de/hardware-hacks/artikel/loeten-in-der-pizzapfanne-kleiner-nachschlag-1406642.html), they expand their approach to soldering BGA devices. Cool idea!
– Matthias