Math.NET Iridium (Numerics)
2008 August Release, Iteration 16 (v2008.8.16.470)
Release Date: 2008-08-14

The following link always points to the newest Math.NET Iridium release:
http://www.mathdotnet.com/downloads/IridiumCurrentRelease.ashxOlder releases and intermediate development builds you'll find in the
Iridium Release Archive.
Math.NET Neodym (Signal Processing)
2008 February Release, Iteration 2 (v2008.2.2.364)
Release Date: 2008-02-03

The following link always points to the newest Math.NET Neodym release:
http://www.mathdotnet.com/downloads/NeodymCurrentRelease.ashxOlder releases and intermediate development builds you'll find in the
Neodym Release Archive.
Math.NET Yttrium (Experimental Symbolics)
Unfortunately there's no public release yet. However, you can grab the current source code directly from the
repository if you're interested.
Math.NET Classic (Classic Symbolics)
Classic has been discontinued in 2003 (in favor of Yttrium), due to some architectural limitations.
Nevertheless, you can download it here if you're interested. I do have plans to relive Math.NET Classic
as it does have some advantages (much simpler, more useful for scenarios where you simply want to parse
and evaluate some expression), but I can't guarantee any point in time.
Version 0.17
Release Date: 2003-07-28

The following link always points to the newest Math.NET Classic release:
http://www.mathdotnet.com/downloads/ClassicCurrentRelease.ashxOlder releases and intermediate development builds you'll find in the
Classic Release Archive.
Verification
Most downloads provide an MD5 hashcode beside of the download link, which you can use to verify that your download was not corrupted. Public keys and fingerprints (i.e. for the assembly strong name cryptographic signature verification) you can find
here.