I've only noticed one particular satellite that travels very fast, OPS 8180 (RADCAT)
circles the earth apparently once every 50 seconds or so.
http://www.infosatellites.com/ops818...orad-6212.html
Seems to be on a permanent orbit, travels through Carina, Volans, Hydrus, Tucana, Sculptor, Aquarius, Pegasus and Lacerta at the moment
Cheers
Chris