There are lots of nice relations in <a href="http://mathworld.wolfram.com/">MathWorld</a>, but you have to search for them in the related pages. For example, if you want to find relations for zeta, or between zeta and gamma, you should visit

http://mathworld.wolfram.com/RiemannZetaFunction.html

and 

http://mathworld.wolfram.com/GammaFunction.html