The following paragraph is justified, using Arial 10 and 1" margins on letter
paper:

A directory which lists participating hospitals will be provided upon
request, without charge as a separate document. Directories are also
available at http://www.eha.md/ (Oregon) and http://www.beechstreet.com/
(Nationwide).

The word spacing on line 1 is normal, while line 2 is quite spread out. I
can make it look right by entering a manual line-break. However, I'd like to
cause it to look right without resorting to brute force.

Any suggestions?