Most of the following sites are not "Dumps" however. They are high traffic sites that list high quality content. If you produce good content, then an easy way to get visitors is to submit it to "LinkDump" sites.
The following list we consider "premium linkdumps" meaning if you can get listed with them, you will gain the a lot of traffic, backlinks, and a killer bandwidth bill.
Covers topics mostly in the tech sector. Web development and science sometimes makes it's way in as well.
Fark -- the founding father of the whole Linkdump genre. Hard to get into but worth a try.
Another huge traffic supplier. Works much like Digg.com but covers a wider variety of subjects.
Pertaining to the strange, humorous, or fun. Great for driving traffic to general entertainment sites.
General entertainment, weird stuff and other BS works with this site. Quick submission. Reddit.com - A bit like a minimalist version of Digg.
DumpaLink.com - Humor, Videos, Entertainment.
LinkDumper.com - General Entertainment, Humor, etc.
DavesDaily.com - Strange, Funny, Pictures, etc.
LinkFilter.net - Not that big in traffic, but seems to be where many bloggers get there news.
RawMeat.com - General Entertainment, humor, games, weird, etc.
Entensity.net - Random BS / General Interest
StumbleUpon.com - social bookmarking toolbar *
Leenks.com - General Entertainment, humor, games, weird, etc.
Zipped.org - General Entertainment, humor, games, weird, etc.
Del.icio.us - social bookmarking *
Furl.net - social bookmarking *
BlinkList - social bookmarking *
MilkandCookies.com - Link Chaos, IMO -- but seems to get decent traffic.
LinkSwarm - General interest, a little bit of everything
Godaddy, NameCheap & more.