Update (8/10 10:30pm): Amazon is offering the Shure PG42-USB Vocal Microphone for $224.95 shipped (Reg. $249, best we can find).
Adorama has an interesting mic combo deal for starter musicians, podcasters and anyone looking to upgrade their recordings. You can grab the Audio-Technica AT2020USB+ Cardioid Condenser USB Microphone with a CAD Audio Acousti-Shield 32 Stand Mounted Acoustic Enclosure for $159 shipped. Combining both items, that’s $121 under the original listings, $98 under the current Amazon prices for both the mic and shield, as well as being the best we can find. Even at the lowest these two items have been offered for, you’re still saving around $50.
This USB condenser mic will certainly offer a much better quality than your internal options with a 16 bit, 44.1/48 kHz A/D conversion and a built-in headphone jack for on-board monitoring. It has received a 4.5/5 star rating from over 75 Amazon customers.
Now that you have a good mic, the only thing that can ruin your recordings is the room you are in. One of the best ways to take the space out of the equation is with an acoustic shield. This CAD option features a perforated stainless steel construction and is made to wrap nicely around the AT without taking up your entire room. This model has a 4.2/5 star rating from over 110 Amazon customers.