LAX Parking

Here is a great site that sources all the major LAX parking lots on one site. You can compare prices all at once instead of searching the multitude of individual parking options.
http://www.airport-la.com/info/parking.html

Another great option is the Fly Away bus, which services Van Nuys (The Valley) Union Station (Downtown LA) and Westwood (the Westside). Park for cheap and take the bus to LAX for only $7.
http://www.lawa.org

Rentals

If you're planning on a long term stay in LA and your friend is sick of you staying on his or her couch...here is a list of furnished and unfurnished rental sites.

Furnished:

Oakwood:
http://www.oakwood.com/furnished-apartments/US/CA/Los-Angeles1.html
Park La Brea:
http://www.parklabrea.com/templates/template_concept04_prime_plb/default.asp?w=parklabrea 

Unfurnished:

Redwood Urban:
http://www.redwoodurban.com/
West Side Rentals:
http://www.westsiderentals.com/ 
Pad Mapper
https://www.padmapper.com/ 

Bed & Breakfast:

Air BnB
https://www.airbnb.com/