As a way to compare these sites, I'll include what each site rates as the top 5 videos for the past 24 hours (where applicable). Please note that I did not pre-screen all of these videos, so watch at your own risk -- some may be NSFW.

Dabble

Dabble is a site that lets users organize playlists of their favorite videos. Their site searches over 21 million clips (and the number is constantly on the rise). Using their playlist data, they keep a list of the most popular videos. Most of their top videos come from YouTube.

1. Arab Men Are Sexy...
2. The Real Arabs !!
3. Arabic Dance
4. Arabic Dance (2)
5. Battle At Kruger

Video Bomb

Video Bomb is a Digg-style social bookmarking site with an emphasis on video. Unfortunately, Video Bomb doesn't really seem to work like Digg, showing only the most watched, most bookmarked, and newest videos... not the most recently popular. Below are the 5 most bookmarked videos on the site.

1. Jesus the Musical
2. Russian parkour (urban extreme gymnastics)
3. Pac Man Re-enacted by Humans
4. Sony Bravia Bouncy Balls Advert
5. Matrix Ping Pong

Vidmeter

Vidmeter creates a daily top 200 ranking of videos from a number of top video sharing sites. The lists are categorized and searchable, and each video has a viewable traffic history. Lists for the past week are available on the site, as well as an all-time list. Vidmeter also operates the video stat tracking service Vidmetrix.

1. Beyonce Loses Top at Toronto concert Deja Vu
2. 1000s FREE TV CHANNELS ON YOUR PC
3. My Chemical Romance - Teenagers
4. Aneta Florczyk's frying pan
5. Best penalty ever!

VDIDDY

VDIDDY lists the top 12 (or so) videos each day for YouTube, Yahoo!, MySpace, Metacafe, Grouper, Google Video, Daily Motion, Break, and AOL Video. For some of these sites it looks like it just grabs the most viewed videos as reported by that site, for others it is less clear what VDIDDY is doing.

WeShow

WeShow is a human powered video guide that organizes videos into more categories than I can repeat here. Not surprisingly, 9 of the top 10 videos over the past 7 days are in the "Sexy" category. Though all are from YouTube, so none are too risqué, be warned that these aren't likely something you boss wants you taking a gander at during work hours. Note that WeShow uses their own, original titles and descriptions for videos and not necessarily what the video was originally called on the sharing site it came from

1. Evangelina Anderson Spins Around
2. Asian Chick Work Out
3. Evangelina Anderson and Mariana de Melo Together
4. Girls Upskirt Mishaps
5. British Large Size Breasts

Gloob.TV

Gloob.TV takes an editorial approach to video aggregation by publishing a daily selection of videos deemed the best by their team of editors. They post a large number of videos each day, so I'll list the most recent 5 at the time of this writing.

1. Dane Cook Hits 2M MySpace Mark
2. Behind the Scenes of 'Balls of Fury'
3. Beyonce’s Wardrobe Malfunctions
4. D-War Movie Trailer
5. Automatic Dorm Par-tay

Mefeedia

Mefeedia aggregates video blogs and web shows from over 15,000 websites and their index include 3.3 million episodes from over 24,000 different video feeds. Below are the top 5 most "faved" of the day.

1. Adelanto Saint Seiya - The Hades Chapter PARTE 10
2. Beach Walk #477 - Duke Kahanamoku Race
3. Beach Walk #478 - Fred’s Fishing Tips
4. Adelanto Saint Seiya - The Hades Chapter PARTE 11
5. Unleashed - Hiatus Fun 2

Videosift

Videosift is another Digg-style aggregator. But unlike Video Bomb, they actually do have a Digg-like daily front page. Below are the top 5 videos currently on the main page as of this writing.

1. Shadow Puppets - Raymond Crowe
2. Deftones - Back to School (Mini Maggit)
3. Stop the bullets. Kill the gun
4. Nailed 'Em - At the Northern Border
5. In Rally Car Talk, This Is Called "Taking the Turn Too Fast"

StumbleUpon Videos

StumbleUpon's Video page is an ever-changing snapshot of the videos that stumblers have given the thumbs up to. Their video page shows 24 recently stumbled videos, but can be refined by tag. Below is a selection of 5 recently stumbled clips.

1. Stop SPP Protest - Union Leader stops provocateurs
2. Waterproof Television Takes On A Firemans Hose
3. Big Train - Jesus and Satan The Office Prankster Sketch
4. Selbstverteidigung
5. John Butler Trio - Get up, Stand up - Taratata

reddit media: videos

reddit's [unofficial] media site is reddit for photos and videos, which of course means the day's top videos are chosen via reddit-style voting. Below are the top 5 currently on the site. Unlike most of the other sites in this round up, reddit media does not embed videos on their site, but instead links to outside sources.

1. Forbidden Lego: the sets that never got released
2. Agent Provocateurs Attempt To Start Riot At PEACEFUL Demonstration
3. Henry Rollins - How I Protest the War
4. Content Aware Resizing
5. Introducing: The Mirror Made Out Of Wood.

Digg / Videos

The best Digg-style video aggregator, is of course Digg itself! Digg aggregates videos the same way it does news, and for videos from YouTube, Google, and Metacafe it plays them in a lightbox directly on the site (for others it just links out). Below are the top 5 newly popular videos at the time of this writing.

1. Girl throws guy trying to steal purse in a suplex
2. Dawkins' documentary, The Enemies of Reason -- Part 2: Health
3. How not to fake technical difficulties
4. Kid Lets Buddy Run Over His Arm
5. Trust Me Im A Professional

Conclusion

For the most part, each of the above sites takes a different approach to aggregating videos and sorting the signal from the noise from among the thousands of videos that are uploaded to sites every day. There appears to be very little cross over on these sites, so using them all will still leave you with an overwhelming number of videos. The trick is to find the one or two aggregators that work best for you (i.e., consistently finds videos that you enjoy).