Of course you could use your “favourite text editor” with Ant, but if you are interested in using an IDE, the following are free and run on most platforms…
Since they are free, download them both and use whichever suits. There is a comparison here from Sun’s point-of-view.
Handy stuff you should have kicking around in your hard drive
All these are seperate libraries that you can download and use. Depending on what you are coding will dictate the libs you require, naturally.