Well, one fairly quick way would be to donate money to SWC if you can afford it -- you receive 1,000 CPs for every $1 US (or foreign equivalent), which can then be exchanged for ships (or credits/vehicles, but ships are the most cost effective) which you can then sell. All donations go directly toward server costs.
Other ways to earn CPs would be by doing other tasks for the Combine - submitting descriptions (there's a link on pretty much every ship/vehicle rules page), planet descriptions, clicking the topsites links on Support the Combine page, GMing a White Scenario, art work for SWC, etc.
Other than that, you're basically stuck working for a faction, and working your way up gradually as most of us had to do. (: Typically factions provide you with a ship to use, so you really haven't got any immediate need for credits anyhow.