Linux

Installed by default on most 32-bit and 64-bit distributions

Windows (32-bit)

Available at
www.slproweb.com/products/Win32OpenSSL.html for 32-bit.

Windows (64-bit)

Not currently supported. Version of 0.9.8b of the library can be build from the source at www.openssl.org/source and is classed as "initial".

Mac OS X (32-bit)

Installed by default.

Mac OS X (64-bit)

Not currently supported. The development branch of the library at www.openssl.org/source has support for this platform.

FreeBSD

Installed by default

Solaris

In the freeware from Sun at
sunfreeware.com for both 32-bit and 64-bit.