Associations can be very good ideas. However, it is just like any other Association or Chamber. There are good ones which are highly active and interactive, and others that just collect your fees but provide minimal support or are simply just not active.
The best thing to do is research them, contact one or two of the members directly and ask them if its been of benefit to them, or just go ahead and sign up (if you can ascertain whether you can get a refund after 30 days if it is not living up to what it says it provides.)
See if they have a list serve, active forums like this one where people are posting and interacting a lot, if they have regular trainings or workshops on their calendar, and so forth. You might also check out LinkedIn. I've found that to be a great resource for information...and often associations have groups on LinkedIn.
Hope these are some helpful ideas to get you on your way.