There's also hmatrix for a pretty nice Haskell API over blas. The one current caveat is that because certain vector code currently uses GSL under the covers, the core hmatrix lib has to be GPL in turn (as GSL is GPL). That said, there's some work underway (by me and some others) to replace the offending pieces of code with some under bsd or other permissive license so that core hmatrix can be rereleased as a bsd licensed lib and thus see broader use.