That depends. Where are you gonna show it?

TVs want a different pixel aspect ratio than computers. Computers want square pixels, and generally 30 fps. CDs or DVDs for 4:3 want 29.97 fps, and a non-square aspect ratio- what these are, I'm not certain of yet, because of the different typesof TVs -- CRT, Flat Screen, and High Definition. Maybe somebody here can fill us in on that.

I know this much so far, and it was hard earned -- for PC video, use square pixel or pixel aspect ratio of 1.0 and use 30 fps. Any other aspect ratio will cause a bounding box, unless you check 'stretch video to size, no bounding box'. Why you'd wanna stretch it is beyond me. Let the codec do it naturally with the correct pixel aspect ratio of 1.0.

If you absolutely have to have the best quality at the smallest size, try these:

MJPEG Not free (but only like $20), can do lossless, can be fast.
HuffYUV Free, lossless, not hugely fast.

I am liking MJPEG-2000 at the moment, it is also a useful codec to have as some cameras output using it. I also had issues with HuffYUV in Vegas.

MJPEG-2000 works great with vegas - you can prerender using it fine and it seems suitable to edit with - I find it doesn't mangle titles like DV seems to.

Hmm, not really the case IMHO. If you want to render something for editing or archival at best possible quality then you want to make as few changes as possible, and pixel aspect ratio is certainly not something I would mess with at that stage. What if the source is tv-like nonsquare pixels (eg from a DV cam) and you convert to square pixels, edit with it then burn it to DVD? You have done nonsquare to square to nonsquare.

Also saying a blanket "30FPS" is wrong. If the source is PAL 25FPS, leave it at PAL 25FPS. Deinterlacing is optional but often it is best to leave it in case you want to do slowmos and reconstruct frames from fields.

Also saying "Any other aspect ratio will cause a bounding box" for PC playback is wrong. If windowed, you will quite possibly never see a bounding box. If fullscreen, it depends on the aspect ratio of the viewer's display. If the move is 4:3 and I am watching on a 16:10 PC widescreen, I will get a vertical letterbox. As long as there is no letterbox actually rendered into the movie, you are good. If you are seeing letterboxes, as long as it is the player adding it and it isn't part of the movie, then you are doing the right thing.

If you are editing it in vegas and you get letterboxes, then the project is probably not matching the footage - the nice thing about vegas (over say premiere pro) is that you can go back later and adjust a projects pixel aspect ratio / resolution etc.

If rendering for the internet, I would recommend again leaving all the settings as per the original. A PC will be able to display any pixel aspect ratio, any framerate, etc etc. Say you put out a DIVX, then if you put that in a DVD player that can play DIVX AVIs from a data CD / DVD, then no pixel aspect ratio conversion / frame rate change / resolution change will have been done, ensuring maximum possible quality throughought the process.