Identifying peaks using a topo map may be difficult, because you need to reconstruct the 3D landscape in your head and decide which mountains are hidden behind others.
So you can fly to the top of your mountain in Google Earth and adjust the tilt to see the panoramic view. This way you get a view, which is very similar to what you'll see in person. Than (or before) you can just identify all visible peaks by using Google Earth labels or a topo map (FYI, if your topo is accurate, you can stretch it over the GE landscape and see it in 3D this way).
Also, sometimes you can find Panoramio photos with labels, or they might just be named like "view of peak X from peak Y".
The next option is to try to find alpinist trip reports, which often have labeled photos. Report sources are usually country-specific, but there are some worldwide catalogues like summit.org.