BackTraxx is OK, but their overall collection is more oriented toward corporate projects than weddings and events. The collection includes two CDs especially slanted toward weddings.
If you like to do your own mix, their "StackTraxx" collections allow you to do so.
Here's one low-cost provider (two day sale, Feb 1/2 only):
http://stock20.com/commerce/index.php
And here's another who has some wedding-oriented material:
http://www.myladonna.com/cd-new.shtml Regards,
Doug Graham