In theory you should be able to install the mono-devel package from Debian, then grab the latest checkout of F#'s Github repository and build. Unfortunately, the most recent versions of Debian's (and Ubuntu's) mono-devel package (3.0.6) include a lovely bug that breaks the F# build (https://bugzilla.xamarin.com/show_bug.cgi?id=10884). Another alternative is installing Debian Sid (unstable branch), where there are currently working F# packages, but installing a whole system from unstable has the sorts of stability issues you might expect, and cherry-picking the right .deb packages from the Debian repositories is unpleasant. There's also the option of using an F# developer's personal repository (https://gist.github.com/tkellogg/5619461), but I don't like adding untrusted sources to my sources.list.
After discovering that Vagrant includes support for a version of Debian Wheezy with F#, I figured out a working, relatively uninvasive approach based on the package