Reading Japanese Online
Did you know that there is software for your computer that lets you simply point the mouse at the kanji and instantly get the definition in English? And best of all, it's totally free! If you don't know how to do this already, here are some detailed instructions.
Install Firefox on your computer
Firefox is a web browser (like Internet Explorer on Windows and Safari on the Mac). It's free to download and use. But most importantly, Firefox has an extensions feature. Extensions are "plug ins" that allow you to add functionality to Firefox. The most important extension for students of Japanese is Rikaichan. Rikaichan allows you to turn on mouseover kanji lookup with the click of a button.
Rikaichan is also freely available. When you set it up (from within Firefox), just make sure to download both the extension and the appropriate dictionary and you're good to go.
Then, when you want to use it, just click the Tools menu and then choose "Richaichan" and you're done. To turn it off, just do the same thing.
If you don't already have it, you can download Firefox below:
Can I use Rikaichan with Internet Explorer on Windows? Or Safari on Mac?
No, it has to be Firefox. Firefox has a special feature called Extensions that allows you to install additional plugins like Rikaichan. Internet Explorer and Safari don't have this capability.
Thankfully, FireFox runs on Windows, Mac, and Linux, so whatever type of computer you have, you should still be able to run it.
When it's not your computer...
The easiest way to get some help reading kanji when you're not on your own computer is to use Rikai.com. At Rikai.com, you type in a site, choose Japanese->English, press enter, and then the page will load-- but when you put your mouse over any kanji, it will automatically look up the compounds for you!
The problem with Rikai.com is that it can't handle links very well, and it performs terribly with multi-page forms. But, if you can't install Firefox for whatever reason, it's worth a shot.