There was at one time a beta underway for SKYPE on the BB, but it has gone silent a couple months ago. I could not see any real benefit however, as it used you minutes to make calls.
And now SKYPE is in a legal battle over patent infringements or something similar. I seriously doubt there will be anything in the near term. You can go tot he Aftermarket section and Search on iskoot (I think that is the name) for a text message app for SKYPE.