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.)
Display, create text file listing info of dead tracks
Play through each track in a playlist at your set interval
Exports and then re-imports selected tracks' artwork
Copy tracks of selected Smart Playlist to iPod playlist
Search allmusic website (AMG) with data from selected or playing track
Use tag data to formulate new file name for selected tracks' files