In node you have access to
To summarize all the the responses: There is no easy way to determine the current Linux distribution.
However here are a few thing you could start with.
uname -vusually gives you a long string with some informations. (E.g.:
#66-Ubuntu SMP Thu Apr 25 03:27:11 UTC 2013)
/etc/debian_version, but this is set in Ubuntu, too!
If you have a list of possible distributions that could happen, you should be able to get that information somehow. If you want a generic approach I'll guess there will be no absolute answer.