Depends on a few factors:
Pre Established Site:
I'd generally put these up on Sitepoint (www.sitepoint.com/marketplace/
) The offers are generally pretty decent there, but it does cost you money to list. If you want to test the waters you can also put it up for free on Digitalpoint (forums.digitalpoint.com)
I always contact the owner of the correct domain name in the situations. Typo's don't need to be misspellings, they could for example be that you own a .com for a large .net domain.
By far the highest selling place for these is Sedo (www.sedo.com
) but unfortunately it can take a while to get noticed.
This is when a domain gets a bunch of type in traffic but isn't necessarily a typo but is most likely a single word or set of words (such as... loan calculator). In this situation I'd consider contacting Moniker (www.moniker.com
) to be in one of their domain name auctions. The costs involved are pretty high but if the domain is good you'll get a great offer for it.
These domains are generally sold to the original owner or their competitor. The general idea is that you sell the domain for twice what you paid for it and a little less than what it'd cost them to get a lawyer to sue you for it. Depending on the site anywhere from $6,000 to $30,000. It all depends on where they are located and how nasty the lawyers fees are.