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.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
Sort purchased tracks into discrete playlists by name or account ID
Export album artwork as folder.jpg to Album folder
Apply selected CD's CD Text to its disc and track tags
Convert or import tracks with any encoder on the fly
Applet assists with swapping, copying, appending data between track tags
Append beginning of selected tracks' filenames with Artist name