What is the best source that you all have found that you have invested dollars in for information regarding points, miles, and/or free travel?

What I mean is this....I received an email to upgrade my points.com membership to gold for $49.95. I would receive 1150 DM miles but I am not sure how else I would benefit. Would the mileage pro book offered in the ads here on flyertalk be a better source? It's $19.95. Free advice is great although we've all heard you get what you pay for. So, what should I pay for? Which source has been helpful to you?

Thanks for sharing your insight.