Weingartner 1927-38, Furtwangler 1942-44, Furtwangler 1948-54, Scherchen 1951-54, Karajan 1951-1955, Toscanini 1950s, Jochum 1950s, Krips late 1950s, Szell 1957-67, Walter 1958-63, Karajan 1963, Bernstein 1960s, Jochum, 1967-69, Solti, early 1970s, Bernstein 1970s, Karajan, 1975-77, Ferencsik 1970s, Hogwood, 1980s, Wand 1985-88, Muti 1980-1992, Karajan mid-1980s, Abbado 1986, Solti 1986-89, Masur late 1980s - early 1990s Harnoncourt 1991, Gardiner 1994, Haitink 1990s, Davis 1990s, Barenboim 1999, Abbado 2000, Abbado 2001, Hickox, 2004, Nelson 2006, Pletnev 2007, Tremblay 2010, Krivine 2011.
Spotify is silently making huge progress on converting their library to 320 kbps, 27 of the 34 sets (one is not available in the UK) are already available in HQ. See log file here.
Here's the Spotify playlist: Beethoven Symphonies Box-sets (35 tracks, total time: 9 hours). It features the opening movement of the Eroica symphony from every set. Use Ctrl (CMD)+G to browse.
I left out some low-budget, outdated recordings, there's no point to spend time on them when you can get most of the other "full price" recordings on Spotify. There's also numerous individual recordings of outstanding Beethoven symphony performances on Spotify, like Kleiber's 7th and Casals' 8th, but we cannot include them here in this index for complete sets.
For American users, only 17 sets are currently available in your place, please uncheck "Hide unplayable tracks" in preferences if you want to browse the full list.
Lastly, a great free ebook: On the performance of Beethoven's symphonies (1900) by Weingartner.