If your camera's shutter can slow down to 1/7.5 or 1/15 second, you can get some cool effects. On my JVC DV5000U, I put on a ND filter and messed around with panning and zooming. The zoom was really interesting. This will also give you the "web cam" look due to the slower shutter looking like a frame rate from most web cams. If your production includes a scene of people conversing via web cams, use a PC LCD monitor that also has analog video inputs. This allows the use of "B" roll on the LCD instead of real web cams. The video will be cleaner and you won't have to transcode any funky video.
Keying snow falling over a scene is another one I have done. If you know how to luma key, this makes sense.
-Shoot the snow fall in daytime.
-Convert the image to B/W.
-Increase the contrast until the gray sky turns black. You may have to adjust brightness, but stay within the 100 IRE limit.
-Split the clip you want to apply the effect to and adjust both snow and main image to the same length.
-Assign the luma key effect to the two clips. If required, adjust luma effect time to match total clip length.
-Adjust the black level of the luma key until the flakes are distinct.
-Now you have it snowing indoors, on the sunny summer beach, or wherever you imagination takes you.
***also, this is how you can have fireworks over any scene.
Be creative. Be unique. Be known.
Keith Breazeal
http://www.kbvp.com