Check out http://www.zhubert.com/. This is an an incredible site, giving online access to the entire New Testament in Greek (the 26th edition of the Nestle-Aland text). If you just hover your cursor over a word you will be given lexical information and parsing help. If you click on a word, you will be given further lexical help, and provided with the option of searching the Greek text for the word (so basically, it's an online Greek concordance). It also links to other sites with more lexical information. More than that, the site also features search options for the ESV, NAS, KJV, and other translations. The author of the site also has a blog, and lots of other interesting stuff that I've yet to discover!
For people who have constant or regular online access, this is one of the best free one-stop shops for study in the Greek text of the New Testament. It's user-friendly enough that you don't have to know much to be able to use it. I expect to return to it often.