[wacheena]

I used to work in the domain business for Google.

Professional parkers value a domain based on its current traffic and ad ctr.

"Premium" domains - whole word .com domains generally have the highest value because 1) users sometimes type them into the address bar, 2) they have a better chance of ending up in organic search results and 3) there is usually clear ad targeting for users who visit the site (leading to a higher ad ctr).

If the domain is exclusively parked, one way to get a very rough estimate of the traffic is to use a keyword search tool. Look at the search volume for keywords in the domain and use that as a measure of how valuable it is.