Solution 1:

I don't think you will find a more feature-rich and well-documented utility/add-on than Hermann Schinagl's Link Shell Extensions found here: http://schinagl.priv.at/nt/hardlinkshellext/hardlinkshellext.html

Truly everthing else that I have read and used pales by comparison.

Solution 2:

NTFS Link provides an explorer extension for creating hard links.

Solution 3:

Have a look at Junction link magic

Solution 4:

Have a look at symlinker.

I haven't found a shell extension to create symbolic links yet (NTFS Link, suggested by Adam, can only create hard links and doesn't have x64 shell support).

Solution 5:

I've used symlinker as well. It's simple if you have a slight understanding of the differences between varying symlinks. It doesn't however scan for symlinks, but I really don't need that function anyway.