According to Matt Grandstaff -
With a pre-order of the game, fans are given a 5-track disc with “featured selections” from the soundtrack, along with a Brotherhood of Steel poster.
We included the front and back sleeve designs for the soundtrack — to get a better look, click on the images to enlarge them. Below is the back sleeve design for the disc. You can see it includes three songs licensed from the 1940’s, as well as two tracks from the game's composer, Inon Zur.
Looking at the 5 tracks - here's a list:
"I Don't Want to Set the World on Fire" by The Ink Spots
"Way Back Home" by Bob Crosby
"Butcher Pete (Part 1)" by Roy Brown
"Fallout 3 Soundtrack" - Main Title (Screen)
"Fallout 3 Soundtrack" - Megaton (City)
GameStop should already have these in stock - so if you've already pre-ordered Fallout 3, go in and ask about it, otherwise, make sure to mention it if you plan on pre-ordering soon.
You can read the article over at The Bethblog