For general job openings: Current open positions at the Space Sciences Lab can be found at the official UC Berkeley Jobs Website, in the External Applicant section. In the left hand menu, under Department, choose Space Sciences Lab [Note: The departments are listed in order of number of job openings, not alphabetically]. Then you can add other keywords if desired.
For post-doctoral positions: Go to Berkeley Recruit, and in the drop-down menu, choose VC Organized Research Units. (You can go to that link directly by choosing the yellow box below).