The rock identification guide I have is an excellent resource. It has beautiful pictures, detailed descriptions and it is well organized, but it is easy to be overwhelmed by minutia and jargon. With words and phrases like hexagonal dipyramidal, sphalerite and chlorite-amphibole-epidote-albite schist, one can feel tempted to not event try to learn.
There are a few great online resources to assist beginners in the identification of rocks. If you want to try, check out these to sources:
The Rock Key at rockhounds.com - This site has an clear dichotomous key, which helps you select the correct rock by making a series of either/ or choices. Some of the steps require advanced equipment like a nail or piece of glass, but you can figure most of it out by just looking at the rock and clicking through. There is good introductory material at the top of the page, and good synopses of the rock types down below.
Rock Galleries at geology.about.com - Sometimes it can be easier to get visual affirmation of the rock type and for that purpose these galleries are a great start. Once you have determined the type of rock (igneous, sedimentary or metamorphic) these galleries have clear pictures of rocks in one location.
Of course these are just a couple resources. If you know of others or have questions about how to use these please leave comments.