I have used various devices to record workshops from HD Videocams to Sony MiniDisc with Sony Digital microphone to Ipod with Voice Recorder addon to Olympus Digital Voice Recorder WS-310M. If you don't need excellent quality you can try the small digital recorders like the olympus. It plugs into USB port and creates windows media files that play in Windows Media Player and can be burned to Cd. Very simple and easy to use. Uses one AAA battery and is size of 2 matchbooks.
If you want excellent quality then it helps to use a better external microphone. I have also used Microsoft OneNote top record direct to Notebook PC using External microphone.
If you use a Mac the SnowBall USB Mic is a great solution to record direct to the computer with USB input.
Many people that create videos use lavalier wireless microphone sthat allow speaker to move around and capture audi direct to videocamera so it stays in synch with the video.
You could start by hiring someone to record an event and talking to them about the gear they use and various options available.