These are my notes on creating a Gerber file from Eagle CadSoft.

1. Open your board file. 
2. Open the CAM processor = File | Cam Processor
3. Open the job file in the CAM Processor = File | Open | Job ...
4. Select "gerber274x.cam" Click on "Process Job"
5. Repeat steps 1-4 but this time run the "excellon.cam" job.

This will create the Gerber files in the same directory as your board files.

For a simple prototype (no silkscreen, no soldermask) I zip these files.

• *.cmp - Component side traces/copper
• *.drd - Drill file
• *.dri - Drill information file (not particularly necessary)
• *.sol - Solder side traces/copper

For final production

• *.cmp - Copper traces component side
• *.drd - Drill file
• *.dri - Drill information file (not particularly necessary)
• *.plc - Silkscreen component side
• *.sol - Copper traces solder side
• *.stc - Solder mask component side
• *.sts - Solder mask solder side

I've found AP Circuits to be a quick and cheap source for prototype boards