A Good microphone and mic accessories (windscreen, a good cable, and a mic stand.)
A Good microphone preamp (This could be included in the audio interface if you choose to use a computer.)
Digital Audio Workstation like Pro Tools. With Pro Tools you get the software, bundled instrument and effects plug-ins, preamps, and the A-D converter. (The digitdesign MBox is a great choice.)
Some good monitors. The M-Audio BX series, and The KRK Rokit series are great for the money. They come in 5, 6, and 8" sizes.
and of course a computer.
A midi interface would be great if your going to be hooking up your keyboard.