Is it possible to upload previously compiled binary? I have a number of sketches that I keep wanting to load into the Arduino but I don't necessarily need to recompile them because I haven't changed anything since the last compile. Since the compile takes a minute or 2 each time, this would save me some waiting.

I can see that the IDE has the option to "Export Compiled Binary", but doesn't seem to have the converse option of Uploading a previously compiled binary. Is there any way to do this?
Yes!
Its possible that you can upload a previously complied binary, using 

AVRDUDE - a command line utility which is actually used to upload binaries, behind the arduino IDE.

You can find AVRDUDE in
Arduino folder > hardware  > tools > avr > bin 

This some documentation for AVRDUDE
http://www.nongnu.org/avrdude/user-manual/avrdude.html

else simplest thing you can do is turn on verbose output during upload and watch for a command in the end with AVRDUDE in it along with the path of hex file, just copy paste &amp;  run the same command in CommandLine; your task is accomplished.