If you want to get a linux/unix machine talking to your GPS unit, most likely you'll be using gpsd. There are many great apps that build off of gpsd such as kismet and gpsdrive.
Installing gpsd on debian/ubuntu systems is as simple as
sudo apt-get install gpsd gpsd-clients
You should be able to connect your gps via serial port and start a gpsd server
The gpsd server reads NMEA sentences from the gps unit and is accessed on port 2947. You can test if everything is working by running a pre-built gpsd client such as xgps.
This is very useful for situations where you need lower-level access to the gps data; for logging your position to a postgres database for example. The debian packages (and most others I'm assuming) come with gps.py, a python interface to gpsd allowing you to pull your lat/long from the gps in real time. This opens the door for all sorts of neat real-time gps apps.
import gps, os, time
session = gps.gps()
# a = altitude, d = date/time, m=mode,
# o=postion/fix, s=status, y=satellites
print ' GPS reading'
print 'latitude ' , session.fix.latitude
print 'longitude ' , session.fix.longitude
print 'time utc ' , session.utc, session.fix.time
print 'altitude ' , session.fix.altitude
print 'eph ' , session.fix.eph
print 'epv ' , session.fix.epv
print 'ept ' , session.fix.ept
print 'speed ' , session.fix.speed
print 'climb ' , session.fix.climb
print ' Satellites (total of', len(session.satellites) , ' in view)'
for i in session.satellites:
print '\t', i
... which gives you a simple readout to the terminal every 3 seconds.
Obviously there are much more interesting applications for this ( logging data to postgis, displaying real-time tracking data in QGIS via a python plugin, etc). But this is a good start for any python based app.