Reading assignment:
If you're feeling ambitious you may want to read the MUSCLE papers (and this one) as well as the ProbCons paper.
I'll go over them in quite a bit of detail on Tuesday, as both describe innovative and interesting MSA algorithms.
Also, chapter 6 in the Durbin book gives an excellent overview of multiple sequence alignment. The multiple sequence alignment chapter in Mount is very useful as well.
Also, I gave a lecture to Jonathan Pevsner's bioinformatics class on MSA and you may find that to be a useful resource, as it covers many available MSA programs and databases that we don't have time to cover here.