Just a few of my fav resources that I use in my own personal research/study, as well as teaching:
Online-literature.com - I have found very,very few pieces of literature that are not included in this beautiful online repository. To search for a particular piece (or even just browse among the authors!) click on the "authors index" link in the first paragraph. In addition to the literature itself, it offers nice author bios, info on particular works, and a discussion forum where lit buffs can wrangle questions about plot, setting, theme, and anything else that catches their fance.
abcteach.com - If I need a worksheet fast and I don't have time to create it from scratch, or if I'm in a bit of an inspiration "slump" and need a fun activity idea, I hit the good folks at abcteach.com. While there are many pages limited to their members (I think membership runs about $30 a year and is probably worth every penny), there is a bevy of pages available for free, which tend towards the colorful and fun!
Of course, I'm a stickler for format, so I love The Owl At Purdue. MLA format made easy!