The American Anthropological Association maintains an extensive database of field schools that is updated regularly. Scroll to the bottom of the page for links to sites with additional archaeology-focused opportunities. The AAA also provides a clearinghouse for internship programs in a variety of areas.
The Archaeological Institute of America maintains a Fieldwork Opportunities Bulletin which lists archaeological field schools
National Science Foundation Research Experiences for Undergraduates (REU) Program: These programs are fully funded and provide stipends. Go to the search page, and either search using keywords or look through all of the listing for Social, Behavioral, and Economic Sciences (which include anthropology and archaeology). Check program dates; many begin before the end of Lawrence's spring term.
Ethnographic Research and Training
University of Florida online courses on research methods in cultural anthropology (graduate level courses open to advanced undergraduates covering text analysis, network analysis, geospatial analysis, behavioral observation, and video analysis); many of these begin May 9!
Andean Community Response to Climate and Social Change (ethnography; Peru): methods in participatory action research and Andean ethnography
Ethnographic Field School (Belize) administered by Center for Applied Anthropology, Northern Kentucy University; departure is May31, meaning you would need to miss 10th week and final exams.
Himalayan Health Exchange (India): Service projects and lectures; not methods training
Isla Mujeres Ethnographic Field School (Mexico)
Off the Beaten Track (ethnography, Malta) includes optional workshops on beekeeping, bread, mapping migrants, fisherman, architecture, and sustainable agriculture)
The Open School of Ethnography & Anthropology (Maya communities, Mexico) ethnographic methods
Archaeological Research and Training
ArchaeoTek Archaeological Techniques and Research Center (Transylvania (Romania)): includes archaeology, osteology, bioarchaeology
Arizona State University Field School (Kampsville, IL; archaeology, bioarchaeology, osteology, GIS)
Belize Valley Archaeological Reconnaissance Project
Caherconnell Archaeological Field School (Ireland)
Crow Canyon Archaeological Center (Colorado; archaeology)
Biological Anthropology Research and Training
DANTA (primate behavior and conservation, Costa Rica)
Dmanisi Paleoanthropology Field School
Koobi Fora (Kenya; hominid paleobiology)
Transylvania Bioarchaeology (Romania; excavation and skeletal analysis)