Lets see....
Reading articles on the internet can really help. You can learn grammar rules from context.
Also, I would buy maybe a little pocket grammar book. A good beginner one is called Barron's Russian Grammar. If you like that one, you could probably buy a little bit bigger one, called "Essentials of Russian Grammar" by Nicholas Maltzoff.
That book may be a bit advanced, but it helps.
Also, I would buy "501 Russian Verbs" book. That helps alot too.
There is also a good website that shows you how any verb conjugates and any noun or adjective declines. It's called Morphological Analysis. Just type in a word and it will show you everything.
http://starling.rinet.ru/morph.htm
Also, it helps to have a good dictionary. I suggest Harper Collins Russian dictionary. Thats the one I use. There is also a couple online ones that are really good. Rambler and Lingvo.
http://lingvo.yandex.ru/
http://www.rambler.ru/dict/