Elijah Hixson helped me with a short list of some of the better known multiple location mss. You can see this referenced, one by one, on lists of New Testament mss. Off the top of his head.
Then in regard to whether there are any composite pics. (Remember the incredible job David W. Danields did on the Sinaiticus composite.Sinaiticus
N (8 or 9 locations)
O (43 leaves in Paris; 1 leaf lost but formerly in Ukraine)
P46 (Michigan and Dublin)
P66 (Switzerland and part of 1 page in Dublin)
P64+P67 (bits of the same manuscript; part in Spain and part in Oxford, and some people think P4 in Paris was also part of it)
P70 I think is in two places
070 is in several
798 is in Athens and Münster
1016 is in Paris and on Mt. Athos, but it is technically a manuscript of Nicetas' Catena on Luke,
Latin purple manuscript that is in 2 or 3 places
I think one of the Gothic manuscripts had a page turn up in a church somewhere.
some Coptic manuscripts being in several places (SA: Alin Suciu would likely know)
The INTF's website will show if a manuscript is in multiple locations, but I don't think you can search for that. In that case, the information is there, but it's a matter of clicking through 5,000 pages and noting whether it turns up just one library or more than one.
Not at the same standards as Sinaiticus. The closest is probably N, where you don't need as careful standards for parts of it. The Vatican section, the British Library section, the Athens leaf and the New York leaf have all been digitized to very high standards, but at the same time, they weren't the same standards adopted by all 4 places.
CSNTM digitized both sections of 798, which would be more ideal, except that they did the Munster part early in their existence and the Athens part more recently. You can tell from the images that they weren't anywhere close to the same high standards they have now when they took the Munster images. The color is all over the place, bouncing between white and yellow, but even without color bars you can tell it's inconsistency in how the photos were taken. There are white gloves in those images (which they NEVER use now), and where the pages are yellow, the gloves are yellow: http://www.csntm.org/manuscript/View/GA_798_INTF