Aside from Camp Erdman's residential cabins, several other buildings and locations in and around its grounds have shown up on LOST. Prime among these is the camp's Assembly Hall. Both the exterior and the interior of this building were used extensively during shooting. The photo below showcases the hall's stone fireplace and also illustrates its proximity to the ocean. For some geographical perspective -- Camp Erdman straddles a highway; on the ocean-side one finds the assembly hall, a few other common buildings, and several groups of residential cabins (that did not appear onscreen). On the other side of the highway lie additional clusters of cabins, some of which appeared onscreen (see previous posts).
The stone fireplace exterior can be spotted in season 5's Namaste, both in 1973 and in 2007. There is also a nice shot of the Assembly Hall on one of the season 5 DVD's special features.
One face of the Assembly Hall doubled as the exterior of DHARMA's processing center for new recruits. A wider shot of the processing center in its 2007 state is shown on a S5 DVD special feature.
The ocean-facing side of the Assembly Hall (which unfortunately I didn't snap a picture of during our tour) served as the DHARMA infirmary exterior.
Although not part of the Assembly Hall proper, the building immediately adjacent to it (you can see the edge of the Assembly Hall fireplace on the far left of the screenshot below) is also featured prominently in Namaste. It is given a celebratory sheen for 1973 and a spooky vibe for 2007.