For my "rig" I've been using a Dell Latitude D800 1.50 GHz laptop with a Pentium M processor and 512 MB of RAM. I've also used a USB microphone and wireless (802.11g) internet connection.
For software I've used SAM Broadcaster, Virtual Audio Cables / Audio Repeater, Skype and Audacity for streaming, recording and post-production of audio. For me the biggest hurdles to overcome have been getting audio settings as they should be so that "both sides" of the conversation can be heard over the stream, "issues" within Skype and post-production itself.
For beginning 'casters, I'd say it's hard to overstate the importance of quality audio from the beginning. Sure you can edit and compress, normalize, and change the volume on your audio, but suffice it to say that editing can be a "non-trivial" task. The way around this, of course, is to work harder at ensuring higher quality video recording in the first place. A big part of this is to not be afraid to mute conference participants and/or to ask them to adjust their audio input settings, or not breathe into the mic, or whatever it may be in a particular instance.
Another recommendation I'd make is to have some podsafe audio standing by for those inevitable instances when you need to take care of some technical details, or are otherwise "multitasking" and don't want to leave your audience listening to dead air.
Also, use the "Skype lady" (by dialing echo123 in Skype) to test your settings and to make sure that you're getting both sides of a conversation. (In SAM Broadcaster, you'll be able to see the audio level meters moving when you and the Skype lady talk--this means you're getting both sides of the conversation). It's also a good idea to listen to the stream itself. Everything may sound fine to you, and those in the Skype conference or skypecast; however, you won't really know what's going on with the stream until you listen.
One last piece of advice I have is to HAVE FUN! There will always be hiccups along the way (hey, after all, it is technology) but it gets easier with time, and there's a very supportive community out there that is ready to help and know exactly what you're going through, from hard-earned personal experience. Good luck and happy webcasting ;-)