The Snowball Ice (not to be confused with Snowball) is an entry-level USB microphone with decent sound quality. It supports cardioid mode only (i.e. picks up all sound from the front of the microphone).
It's on sale for $68 at HN - not the cheapest price ever on OzBargain but it is the cheapest price ever for Amazon according to camelcamelcamel. Amazon has it listed at the same price at the moment but it's out of stock in stock 20 Aug - credit to FrontBottom
I use this almost every day and would highly recommend if you are doing video calls/presentations. Sound quality is much better than headset mic. Only drawback is the tilt, as it doesn't angle high enough to be used on lower height desks.
edit: Height of stand is approx 10.5cm fully extended and max tilt is ~30 degrees to those who are wondering