I am asked frequently enough where one should volunteer to excavate in Israel. My best answer is that they should look at the January issue of Biblical Archaeology Review, which gives a round-up of the coming summer excavations.
BAR just made it better by putting the "article" online. This allows non-subscribers to easily see the information, and it allows the information to be quickly updated should circumstances warrant (as was already necessary with the Mt. Zion dig).
FindaDig.com is an easy-to-remember website which includes a list of excavations categorized by region, and listing details such as excavation dates, costs, housing, contact info, and application details. It also lists relevant articles in BAR, which any participant should read before the dig. Overall, it's a terrific contribution for any interested in biblical archaeology!
I do find a strange irony that the Gath dig is listed as "Tell es-Safi/Gath," whereas the Bethsaida dig is listed simply as "Bethsaida." I don't think anyone doubts the identification of Tell es-Safi as Gath, but almost no one besides the excavation team believes that et-Tell is really Bethsaida.