Resources
Books
The Powerscore books are also a helpful resource. Having said that, we have some criticisms of them (which you can read here and here). The Powerscore books are also cheapest at Amazon and most people find the Logical Reasoning Bible and the Logic Games Bible to be most helpful.
Practice Tests
The most important resources to help you study for the LSAT are real, genuine, LSAT questions. The simplest and cheapest way to get 30 real , (mostly) modern LSATs (post 1991), are to buy the 10 Actual LSATS Volume V the Next 10 Actual LSATs, the 10 New Actual LSATs, and 10 Actual, Official LSATs Volume VI. These will provide you with enough questions to last you for some time.
Other Resources
Law School Predictor is also helpful, as is the LSAC version of the same thing. Both are useful, but please remember that these are approximations and that numbers are not the only thing law schools look at.