Diffie Hellman, use to be patented. That patent has expired making it the first public key cryptographic algorithm unencumbered by intellectual property issues.

The RSA algorithms are patented in the United States. Outside of the United States there are no patent or royalty restrictions on the use of RSA. This is why, legally, RSAREF is required in the United States for any non-commercial use of the RSA algorithms. The RSA patent expires in another couple of years. Due to export restrictions, RSAREF should NOT be used in any development outside of the US.

IDEA, the symetric algorithm from Switzerland used in PGP, is copyrighted in Switzerland and the US as well as other countries which permit copyrighting algorithms. Germany does not.

Blowfish was explicitly placed in the public domain by its inventor, Bruce Schneier. It is neither copyrighted nor patented.

RC4 was held as a trade secret by RSA Labs until someone reverse engineered it. A trade secret is the most ephemeral of the intellectual property types. Once it's gone, it's gone. ARC4 (Alleged RC4) is the publicly available algorithm which, for all intents and purposes, appears to be completely compatible with the RSA RC4.

Until recently SkipJack the algorithm at the heart of the Clipper Chip was a closely guarded classified algorithm. Due to a logistical screwup, certain government agencies found themselves required to use Skipjack for certain communications long before it was going to be available. The NSA was forced to release SkipJack and make it available for integration into products to support the mandated needs of government agencies. They did it to themselves.