Frequently I come across a sum (either finite or infinite, and often in the context of moments of discrete random variables) and unless I can force it into one of the few forms that I know, such as a geometric series, sum of a known probability mass function, or a known Taylor series, I am stumped. I feel that my lack of skill with the machinery of summation is holding me back.
Are there any good resources out there, either free or not, containing a large number of worked examples? I'm aware of such resources for calculus/integration, such as Schaum's 3000 solved problems in calculus, but I haven't seen any for sums.