Depending on your current level in Spanish, there's a book that I used at times. Spanish, just like any other language, has rules and then random exceptions to those rules. Not just with irregular verbs, but syntax, and ideas that simply don't translate (for example, saying "Tengo una amiga vieja" is NOT the same as "Tengo una vieja amiga").
Check out this book, "1001 Pitfalls in Spanish"
http://www.amazon.com/1001-Pitfalls-Spanish-Marion-Holt/dp/0764143476/ref=sr_1_1?ie=UTF8&qid=1358545910&sr=8-1&keywords=1001+pitfalls+in+spanish
It has more than one edition, I believe, since it's been around for a while. It's a very good resource and pretty inexpensive (FYI- There's a Kindle version on Amazon of this book for US$7.50).
The only thing to remember is that this book has "Español" in mind, but not Castellano. How helpful you find this book to be depends in part if you plan on using the language principally in Argentina or elsewhere in the Spanish-speaking world. In any case, it's still a very helpful resource!