This community as well as Wet Web Media are two I have found to have particularly good advice.
Some people can get away with water changes once a month if they have a very light bio-load (small fish, not a lot of fish, not messy feeders, not fish that produce a lot of waste, and no overfeeding). This also works better in a larger aquarium, say 50 gallons, as it is much more forgiving.
I am a fan of Living Sea. They have a good selection, and even offer classes to help out beginners and advanced aquarists alike. True, I've heard horror stories of them selling fish way too large for home tanks, and a few of their employees have been a little less than polite, but then you have the employees that are more than polite, very helpful, and eager to have you set up the aquarium of your dreams, and if you're looking for that hard to find fish, well.. they have a good chance of having it.
You can even smell the salt from a couple blocks away.
My advice is to not take advice from a LFS
. Sometimes a good store will have a bad employee, and lose your business because they were not aware of one of the mistakes of their new hires.