Well i'd say the sound source, the room, the mic, the pre, in that order of importance. Mics are like as personal as a pair of pants that fit right, sometimes cheap mics work phenomenally on some vocalists. So just test some at a local store and pick the one that flatters your voice, or makes you 'sound like you' on the recording. I suggest you use the standard shure sm57/58 as a benchmark, cuz those mics just kill.
this leaves you w/ a plethora of choices for an 'interface' Depending on your setup which you should surely define, just pick the one that has features you want need. sound quality is generally about the same in this range, and is pretty good. Look into tascam, m-audio, focusrite, and plenty of others. hope this helps put you in the right direction!

-kyle

If you want to record to something (like singing over backing tracks) you will want an audio interface for the low latency monitoring. In that case it will be your ADC and DAC in one unit and you won't use whatever DAC you have during tracking. You can use it during mixing if you prefer it.

For just recording spoken word or a capella singing then you don't need to be as concerned about input monitoring and you could consider a USB mic. But I would still recommend a separate mic and interface so you can try other mics later on.

You can hardly do better for a vocal microphone than with the venerable SHURE SM58 with an additional foam pop filter. So for $100 you get a microphone that can compete with a $3000 German Neumann U87, and not sounding too much different from that $3000 top shelf microphone. I use them interchangeably with singers and announcers. Where I may have one announcer on the $3000 microphone, and another on the 58, and they match very closely. You might need a little, 2 DB boost at 10-12 kHz with the SM58. And some high pass filtering. If you don't want to use that 2 DB boost? Then get yourself a Beta 58 instead of the SM58. And that extra condenser like high-end will be there in the Beta 58. There is a reason why this is one of the world's most popular recording and PA microphones. You might think others sound better, but nothing sounds as good as a 58, SM or Beta. And I own extremely expensive than collector microphones like the Neumann tube 67's, KM 56 tube, 87 transistor, KM 86 transistor, RCA and Beyer ribbon microphones, SHURE SM 81 electret SDC and what do I grab for most often? The SM57/58's and not even the Beta's, though I do have a couple of those also. This might sound like a commercial for SHURE, but I don't work for them. They work for me!

OK, all of you, SHURE microphones, ATTENTION! Thank you, at ease. So if you want a military quality microphone tank, go for the one you can nail in nails with. You can't do that with a condenser microphone of any kind. I would just like to drop a SM57/58 from the top of the Empire State building, and still find it working. 1100 feet down. You can even run over them with your car, and they keep working. But don't stick them in your oven during Thanksgiving. Otherwise you will turn the microphone into a turkey.

I like a hot corned beef on rye with lots of mustard. Yellow or brown, mustard. I'll even take it with coleslaw, Swiss cheese and Russian dressing. MMM MM! Yeah. I need the cholesterol.

Isn't the Cholesterol a musical instrument?
Mx. Remy Ann David