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 Script Editor (AppleScript Editor pre-OS X 10.0) which is located in your /Applications/Utilities/ folder. More information is here.)
Convert selected tracks and export the converted files to a new folder
Two scripts copy text from clipboard to current or single selected track's lyrics tag
Remove iTunes tracks disassociated from files
Display, create text file listing info of dead tracks
Minimize and re-set position of iTunes
Displays files in iTunes Media folder not in iTunes track library