A couple of great resources for this:
DarkMark's Comic Indexing Domain:
http://darkmark6.tripod.com/indexintro.htmlThis is a full index of the Earth 1 Superboy, Superman, Supergirl, and related family. This is patterned after the ICG DC Indexes by Murray Ward, and includes input from Murray Ward, Mark Waid, and Mike Tiefenbacher (of The Comic Reader fame). It does not overlap the published indexes, so it leaves out the Legion of Super-Hero appearances before the last couple of Action issues, and leaves out the JLA appearances. It is otherwise quite thorough (the first Superboy file even has a full chronology of Krypton in it).
Tht other resource is Mike's Amazing World of DC Comics-The DC Indexes:
http://www.dcindexes.com/indexes/index.phpThis is in the same general style as the other site, but a little harder to read and navigate (but includes cover images and credits). The other site doesn't cover Earth 2; this one does. In the Earth 2 section, click on Superman (or Lois Lane), then click on the APPEARANCES button at the top. This then lists all the issues; each one of which is clickable to get the details.