Sure, iTunes can join tracks, but only if they're consecutive CD tracks, and you haven't imported them. This script allows you to join any two (or more) MP3 tracks (repeat: MP3 tracks only), provided that they are the same format and bitrate.
Also see Join Together, an application that will join any type of files.
Perhaps Also of Interest...
downloaded 10m 12s ago
Remove iTunes tracks disassociated from files
downloaded 10m 16s ago
Add or subtract a user-entered number from each selected track's Skip Count
downloaded 19m 33s ago
Set the Plays of selected tracks.
downloaded 21m 50s ago
Set choice of various number tags of selected tracks incrementally
downloaded 26m 15s ago
Apply selected CD's CD Text to its disc and track tags
downloaded 43m 51s ago
Deletes the lyrics of every track in the Music playlist