Flash is good for creating, but you cannot directly import it into Vegas. If the software you are using to create flash with supports it, export your animation to .AVI. Swish has this feature and it's very cheap!
Swishzone.com You can try the demo for free, but until you've paid for a registered copy, the text in your output will be scrambled.
I find ULead's PhotoImpact to be really useful for doing various masks, title bars, and titles. I also use Swish with blue screen to do animated titles and graphics. Swish is $49.95 and you can get PhotoImpact for around $60. PhotoImpact does nice shadowing with transparency and has more controls than the titles in VV3. For example, you can do 3D rounded titles with gradients or other material backgrounds. PhotoImpact also has lots of shapes and other sorts of "paths" that can be 3D or flat with or without shadows and can do text that follows a path in just about any shape. I find PhotoImpact, Swish, and VV3 to be a nice combination. Swish can save as a 720x480 AVI quite nicely with any color background. Then the chromakey filter can be used to make the background transparent. You can do all sorts of pretty fancy animated titles and graphics with very little learning curve and very little cost.