From the Mobissimo Newsletter:

In addition to adding travel suppliers, we have launched a new product this week – MobiCombo. Often, flying to Europe and other destinations is cheaper when you buy two tickets. For example, during the summer months, direct airfare to travel hotspots like Croatia and Greece is much more expensive than buying two tickets. Buy one ticket to a major hub like London, then switch airlines (and sometimes airports) to a low cost carrier like EasyJet or Ryanair. The savings can be hundreds of dollars and your itinerary can be much more flexible.

Check out MobiCombo.

Eventually, I assume Mobissimo will offer this service automatically. Instead, as you can see in the directions, a user currently has to 1) search for a direct flight and write down the price, 2) search for a a flight into a major European hub and write down that price, 3) search for a flight from the hub into the city of choice and write down that price, and 4) add up the 2 prices (from steps 2 & 3) and compare that price to the price of the direct flight (step 1). Still with me? Didn’t think so!