Click on the Google Street View image below and then keep clicking on the street ahead to take a virtual trip down Commonwealth Avenue.
Search for a building by name or address in Google Images. Put the name or address in quotation marks to search for the exact phrase. When using an address, add Boston (outside the quotation marks) so you don't get, for example, 871 Commonwealth Avenue in Venice, California. (Yes, there is one there.)
NOTE: That you can also filter Google image searches to image that are labeled for reuse.
Flickr lets you search for images of BU that have a Creative Commons license governing their use. (About Creative Commons on Flickr)