That is the worst solder job I have ever seen. I can't believe the solder fell off the PC board and the pins!
Ground yourself to keep static electricity from the board. Clean all the old flux off the area as gently as you can. Then use a good quality rosin core solder to resolder the pins to the traces on the board. Be as accurate and quick as you can. You don't want the RIOT to get overheated yet you want a good solder connection.
When you are done make sure no solder has flowed to/touched traces and pins it shouldn't.
Edited by jdrose, Sat Jan 28, 2012 12:29 PM.