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.)
Enter text for the selected tracks' Category tag
Set the Plays of selected tracks.
Use tag data to formulate new file name for selected tracks' files
Perform search-and-replace on text in your choice of tags
Two scripts create discrete playlists of all HD or all SD videos
Remove iTunes tracks disassociated from files