Being that I am trying new software all of the time for work, I can usually get extended key codes/serialz by just shooting them an email.
Now if the software is new and still in beta, and it looks like something I will buy, I barter to get the price even lower.
For all of you M$ guys out there, you can download almost all MS apps for a 180 day trial period.
Now, if you do happen to have a bit of cash to spend, join TechNet. You get a boatload of software, plus great tech bulletins.