Brian has two very nice posts on the basic syntax of F#.

The basic syntax of F# - keywords and constructs

The basic syntax of F# - classes, interfaces, and members

I have written lots of blog entries about F#, but I haven't yet described the basic syntax of the language!  So today I'll try to remedy that, describing about a dozen keywords/syntactic-forms that you will most commonly encounter when reading F# code.  This blog entry won't cover all the syntax, but it covers perhaps the most common 75% or so...

and then

Today's blog entry covers the F# syntax for authoring classes, interfaces, and members.  Together with the previous blog entry, this probably covers the most common 90% or so of the language.