I use Hypercam. It's basic, functional, free, and stable. All the editing happens in Vegas. It's a little tricky to figure out how to capture audio into Hypercam, I need to use two interfaces and patch them together with cables. Hypercam uses WDM on one interface, Sonar uses ASIO on the other. There are ways to use a single interface, but I find that ultimately, the dual interface option is more straightforward.
For the videos, I actually had to write out instructions on how to set the audio in Vegas, Hypercam, the interfaces, and the Windows control panel. Before doing any videos, I go trough the checklist as all the variables need to be set up correctly.