There are some apps I can find on app brain and when I try to open it in the market it says its not there. Is att blocking them or what?
More likely your version of Android. You'll only see apps that apply to your OS version in the Market.
Not necessarily... I do remember a while back hearing that AT&T was blocking "WHERE" from the Market, so the carriers do have SOME power. But AppBrain, when coupled with Fast App Install, can usually work around it. (I, for example, downloaded Flash before Verizon released that second Froyo update for the OG Droid that enabled me to do that.)