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.
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downloaded 2m 19s ago
Droplet adds files, creates playlists based on folder name(s)
downloaded 6m 22s ago
Sort purchased tracks into discrete playlists by name or Apple ID
downloaded 9m 24s ago
Copy chosen tag info from one set of tracks to a different set of tracks
downloaded 10m 38s ago
Exports and then re-imports selected tracks' artwork
downloaded 13m 9s ago
Create two playlists containing tracks with JPEG and PNG artwork
downloaded 15m 16s ago
Export artwork of selected tracks to parent or specified folder