Halo 3 ODST audio log locations (first 15). First head to Kikowani station, I recommend getting all the audio logs when you have either finished the game or just before the last mission.
I managed to steal the ghost off of a passing grunt but you can get a mongoose from one of your super caches. You'll unlock the super caches when you get a certain number of collectibles.

For audio logs 16 - 29: http://youtube.com/watch?v=aI_IAdZpyBs
For audio log 30: http://youtube.com/watch?v=H15-6xI40YY
For just the map of all 29 audio logs: http://youtube.com/watch?v=l_ZDHPm3oYc
For more ODST videos: http://halo3odstvideos.com

Please note: I already got one collectible before I started. Sorry for any confusion! (less info)