VirtualDub is on my list of most useful programs ever. A big thank-you to Avery Lee for making this program and for making it available for free. If you're into video editing, you want this! You can also download the VirtualDub filter SDK here, necessary for compiling the filter source code.
Jim Casaburi, independently from my own efforts, wrote two noise reduction filters based on similar principles to the ones employed in SNR and DNR. His filters are slower, but offer more options.
Huffyuv, is a high-speed lossless video codec written by Ben Rudiak Gould. I use it for all my captures.
Huffyuv Revisited, is an updated version of Huffyuv above. This implements some features missing from Huffyuv and improved speed.
Bt8xx WDM Video Acquisition Driver is an Open Source project to create a video capture driver for boards based on the common Brooktree Bt848/849/878/879 chipsets. For me, capturing video under Windows ME, 2000 and XP was almost impossible until I tried this driver.