Actually at present, even if you were to get the correct URL with URL Snooper, it would do you no good; imeem.com uses "anti-leech technology", which means that they send your web browser a temporary link to the media file that can only be accessed ONCE. Thus when your web browser gets the link, it then plays the music/media file just fine, but if you try to start another download from your computer to capture the media file to disk, the imeem.com server will refuse the second request.
The only freeware programs I know of that can circumvent the "anti-leech technology" are Orbit Downloader and Free Music Zilla. Both of those programs can download easily from imeem.com.