You can make it look crappy in an artistic way. If you're into still photography, there's a cult-ish following for the Holga camera (~$30 medium format) and other toy cameras. The "great" thing about these cameras is that they add vignetting, have random light leaks (which may be cool), and soft images.

I personally like Holga images which include the scan of the film itself (i.e. you can read the text Kodak blah blah blah with the sprockets and everything). Unfortunately video doesn't have this, although if you want you could take a picture of your camera and put the video in the LCD screen.

In Vegas:
Add vignetting:
Create a new layer on top of your video.
Add the color gradient filter.
The middle color should be 128 128 128 neutral gray, the outside 0 0 0.
Change composite mode to overlay. (Other ones work too.)
To vary the strength of the effect, you can change the values of the color gradient. You can also add the brightness and contrast filter and reduce contrast.
Or you can change the opacity of the track.

If you want to keep the composite mode self-contained, move the footage and the gradient to lower layers. Use the parent//child relationships so the composite mode only affects its child tracks.

You can also add additional points onto the vignette to add a color cast if you like.


Add film-like gamma response:
Take the color curves filter, and add a s-shaped curve. Drag the 'handles' on the top and bottom and make it look like a tilted S.

Trick effects:
If you play with the channel blend filter, you can map parts of R/G/B channels to other colors to bend the color palette a little. You can do similar thinks with the secondary color corrector.

You can get pretty "punchy" saturation as follows:
Add saturation adjust filter
Push the amount slider up.
Drag the "low" slider DOWN. If most of your image has saturated colors, this will create less saturated colors in some parts of the image and create like a saturation contrast.

To hide compression artifacts, diffusion effects work great. Example:
Duplicate video onto itself
Set upper track to overlay compositing mode.
Add gaussian blur to the top layer.

And... whatever else you can think of.