One of my favorite sites is MusiChristian.com! The music is usually priced much less than it is on other sites, AND the shipping costs are normally very reasonable. They also have a some great bargains that are usually too good to pass up...and they make GREAT Christmas gifts!! What's not to love???
Plus: a lot of times you can find some awesome exclusive bonuses, like this autographed Chris Tomlin CD with a bonus music sampler for just $7.77!