A large part of growing your audience is by letting them see you. Even if you have a face for radio, allowing your new found fans to see and interact with you brings a new dimension to a stream. With programs like the aforementioned Flash Media Encoder or Xsplit, you can create a picture-in-picture display where the world can see every grimace and victory smirk bubbling inside. 

Logitech has an awesome line of affordable webcams that shoot in HD. And if you really want to nerd out, go for the FaceVision FV Touchcam N1 and V1 models. They're hailed for handling low light and giving incredible picture quality. The FV Touchcams are also certified by Skype and that co-sign means a lot as not too many webcams out there can boast it.

Logitech HD Pro Webcam C910
Price: $109
Buy it here: amazon.com

Logitech Broadcaster Wi-Fi Webcam
Price: $200
Buy it here: amazon.com

FaceVision FV Touchcam N1
Price: $120
Buy it here: facevision.com

FaceVision FV Touchcam V1
Price: $60
Buy it here: amazon.com