Satellites

Denver area

Try Spot The Station from NASA for emailed alerts (Will require your specific location):

http://spotthestation.nasa.gov/

For satellite passages specifically over Denver, use these links:

http://goo.gl/IdBb8r (NASA)

http://goo.gl/LKy2I6 (Spaceweather)

http://goo.gl/sC7syH (Heavens Above)

For satellite passages specifically over Aurora, please use:

http://goo.gl/yXemdB (NASA)

http://goo.gl/N0U1lo (Spaceweather)

http://goo.gl/kCseNB (Heavens Above)

Elsewhere

Try Spot the Station from NASA for emailed alerts: http://spotthestation.nasa.gov/

http://www.jsc.nasa.gov/sightings

Spaceweather.com Flybys site: http://www.spaceweather.com/flybys/ [US & Canada]

http://www.spaceweather.com/flybys/country.php [worldwide]

Twisst personalized Twitter predictions:

http://twisst.nl/

Heavens Above (ISS, Iridium flares and much more):

http://heavens-above.com/ [worldwide]

Realtime Satellite Tracking

http://www.n2yo.com

All of the above will require your location information