I have a 5 hour layover in Brussels. Any suggestions as to what to go see or do?

Agree that 5 hours is not a lot. From the airport, the easiest and fastest way is to take the train to Central Station (a train every 20 minutes), then walk to Grand Place indeed.

The beer suggestion is good ... you have a choice of 300 different Belgian beers at one of the pubs on the Grand Place... In case you don't like beer, you may walk to see Manneken Pis, a local celebrity, or the square of the Sablon, with many antiques shops. If you are an art lover, you may go and see the museum of fine arts (still in walking distance) Flemish primitives painters, or 20th century surrealists (Magritte) are among the most interesting things to see there. In case you like music instruments, there is a wonderful museum for music instruments not far from there. Still, you may walk to the Brussels Park and have a look at the king's palace. Then go back to central station and take a train to the airport !

Some interesting data on this link : http://travel.yahoo.com/p-travelguide-191501719-br...

Thats Brussels airport? Not too much time to do anything.

Get a bus or tram to the centre, go to the central square, try several Belgian beers, and head on back.