I use Notepad++ as more or less a Notepad replacement and for simple code viewing and writing.
For bigger programs I use JEdit. I don't like that the executable is a .jar though, since I can't seem to get it to associate with files easily if the context menu is not used.
For JEdit plugins, I only use right now:
EditorScheme
BufferTabs
As Sunner said, there are tons of handy ones.