Four main sources of aerial photographs are:
Local Government Websites - To find high resolution airphotos, check state & local government websites first.
Historic Aerials - Online historic aerial photos for purchase.
The National Map - The best site to download high-resolution, mostly-recent aerial photographs in TIFF format. Zoom-in to the area of interest, and then select "download"able layers, select area, and then download.
USGS National Maps Viewer - Offers very similar to what NM Seamless Servers offers, but different interface. Images can be downloaded in various formats (TIFF, IMG, JPG, JPG2000). Consult this help page!