ABX Logistik x-bag - this will cost about €1,000 for almost 300kg, which is not too bad. You drop your stuff off at the airport and then pick it up from the cargo company on the other end, and your rate is dependent on the city. The per kilo price goes down once you have more than 100kg of stuff. Definitely check it out, though they only ship to select cities.
Note: ABX do not ship personal household goods. They only do commercial shipping. It's not clear whether this has always been the policy or whether it's a recent change. As of Summer 2006 they were not shipping personal items.
External links: