Recent theses are available online via ProQuest, and a smattering of older ones are stored on this website. It doesn't seem possible to link directly to ProQuest's list of Berkeley Astronomy ones in particular, but there are a few ways to quickly find what you want. As of June 2012, you can search for a thesis by author like this:
And you can browse Berkeley astronomy theses like this:
Below is a very incomplete listing of Berkeley theses. The format is indicated in brackets, with “[PQ]” indicating a link to ProQuest. “(P)” after a name denotes a degree received in Physics. “(AST)” after a name denotes a degree received in Applied Science & Technology. Some of the direct file links are quite large, unsurprisingly, though others link only to abstracts.