Where and How to Buy Tickets

Admission.com
While Admission.com is the official source for Senators tickets, it's not exactly a reliable one. First of all they sell out almost immediately for all the good games. Secondly, their web site is a pain to use and sometimes it just shuts down entirely while you're shopping.

TicketLiquidator
The best place I've found to go is TicketLiquidator.com. They have an enormous variety of tickets to choose from, and the prices aren't very much different from regular box office prices. This is an especially good resource if you want center ice seats for a playoffs game. They won't be cheap, but I guarantee they'll have them.

E-Bay
Ebay is another good place to look for tickets that are supposedly sold out. The only caveat here is that you never know who you're dealing with, and there are no guarantees.