[SammoJ]

I have also used libsvm a lot and can heartily recommend it - but only for non-linear kernels. If you wish to use a linear SVM (which if you aren't familiar with machine learning you should probably try first) then for your own sake try libocas:

http://cmp.felk.cvut.cz/~xfrancv/ocas/html/

It uses SVM light format and also has a mex wrapper (MATLAB). More importantly I found that for linear SVMs it was around 100-1000 times faster than libsvm (I shit ye not).