scanmem is a debugging utility designed to isolate the address of an arbitrary variable in an executing process. scanmem simply needs to be told the pid of the process and the value of the variable at several different times. After several scans of the process, scanmem isolates the position of the variable and allows you to modify its value.
httpdbg is an HTTP proxy server which is single-threaded and prints every HTTP request and response to a log file as well as to stdout. It effectively single-threads your browser, which can help in debugging race conditions.