It depends what your mission is, but the short and skinny...

Musician > Mics > Cables > Signal Processing > Cables > Interface > Cables > Software > Cables > Monitors.

Add in a dedicated hard drive to record/playback the audio.

A simpler version of GFs list:

Musician > Mics > XLR cables > Interface > Firewire (or USB) > Computer
Most interfaces have built-in preamps (signal processors).

Then of course whatever DAW software you want.
Many interfaces come bundled w/ "light" versions of very reputable DAWs.
A firewire interface is preferable to one that uses USB to connect, and using the computer's built-in soundcard is NOT recommended.

Finally, you need a way to monitor what's going on.
Active monitors or passive monitors (w/ an amp for the monitors) are preferred, but you can get by w/ good headphones. I recommend you DO NOT use computer speakers for monitoring.

If you have any more questions, please let us know.
I do recommend that you do your homework first. A well-researched, well-formulated, specific question gets better answers.
People here are more than willing to help, so long as you help yourself first, and answer the obvious questions for yourself.
Not to say that you don't, just a few pointers to help you make the most of these forums.