I did a review of the large diaphragm condenser mic called the AT2035, by Audio-Technica. To really step up the quality of your audio firmly into the professional zone, you need to have a large diaphragm condenser microphone (sometimes called an LDC mic), especially if you will be recording voices, both for music and for voice over purposes.
Audio-Technica is a respected manufacturer of good quality mics, and if you can only afford to spend less than $100 on one of these types of mics, you can grab their AT2020 for about $65 (really good price for a mic like this). But if you can afford to spring for the extra 85 dollars or so, I highly recommend going with the AT2035, costing $149. It is quieter, more sensitive, and gets better low-frequency response than the AT2020, plus it comes with a shock-mount and has switches for rolling off low frequencies (a high-pass filter at 80Hz) and lowering the output by 10dB with a pad switch.
Check out the post with the review of the AT2035
, which also has some audio samples in a mini-shot-out with the Rode NT2-A