I believe that www.sitepoint.com has a forum for selling templates. If your template has never been sold elsewhere before, you might consider using www.themeforest.net as well. You won't get $400 up front, but good templates can make that much and more after awhile.
Interesting. Do you (or anyone else reading this) have any experience there as far as how well it works, how popular it is, etc etc..?
Themeforest I mean.
it's basically simple, you just have to create a correct template(in all aspects...design, aesthetics etc) which gets accepted by their reviewers then it goes on sale & can be sold infinite times, the selling price usually is around $10 per sale for an uncoded psd template & arnd $35 for a coded one, if the template is really good....well it can sell quite a lot of times.