Some of the best ones I have found are the Swipes product from Digital Juice. They certainly aren't free but they often offer deals if you by several. They work well with Vegas and cover a wide variety of themes.
check this site please. They're offering some nice transitions for 29.-$. A trial is available as well to check whether that's what you're looking for.
proDAD GmbH today announced the availability of free downloadable “Starter Kits” of its popular Adorage and Vitascene effects products. The Starter Kits are not trial or demo versions, they contain fully functional effects and transitions as well as plug-ins to allow the effects to be used seamlessly in popular NLE applications from Adobe, AVID, Corel, Canopus, Magix, and Sony.
Note that Vitascene is not supported within Sony Vegas Movie Studio (only the "pro" version of Vegas). In my experience the transitions and effects work (sometimes workarounds are needed), by VMS tends to be detabilized.
These are free. You may have to wait 1-4 days for them to return you with the actual download link.
Thanks for the link to the proDAD starter kits! The message after registration seems to imply that the download links will be in my inbox immediately, but I'll wait as you said...might be a few days before I get a response.
Thanks for the link. I just might grab those for myself. I already have a bunch of the DJ Swipes and I also have ProDad Adorage but I seem to be obsessed with collecting more tools.