How to purchase an OST? Can anyone point me in the direction of a legal online seller of OSTs? There are a few anime and OVAs that I want to own but I have no idea where to search? 

A link or two would be upvoted.
There is of course Amazon  That links to a soundtracks search that brings up Anime OSTs............and games for some reason.

There is cdJapan

Those are the ones I have used.