I heard someone was looking to burn extra coins here.
A provably unspendable burn address is mfWxJ45yp2SFn7UciZyNpvDKrzbhyfKrY8
How did I get there?
First, you have to download and compile
https://github.com/casascius/Bitcoin-Address-Utility (including it's dependencies. they aren't hard to find). Next, change line 402 of Form1.cs from
case "testnet": return 111;
to
case "testnet": return 25; //you can get this number from base58.h of glowcoin's source. it's the publickey hash verison
Then, compile it and run it. Click on address utility. In the bottom text box paste the address mfWxJ45yp2SFn7UciZyNpvDKrzbhyfKrY8. Then, push the up arrow button directly above the text box. This takes the base58 encoded hash and turns it back into the actual data within the address. This data will be 0000000000000000000000000000000000000000.
I didn't actually test that this is a valid address and all, but I assume it is. If I did something wrong please tell me