www.ka72.com/ also reads .sbp files.
These files may (usually, really) have several sessions in them. Most software, including Realspeed, will split the file into separate sessions.
You can use GPSBabel (but only really recent versions of it) to convert .SBP files into another format, but you really shouldn't. .SBP files have lots of good information in them, including SDOP data, which give them greater precision than most of the formats that GPSBabel will convert them to.
Cheers,
Dylan.