IEEE does important things to support researchers and practicing engineers. Computer Society is their group for software developers. I used to read their flagship journal, IEEE Spectrum almost cover to cover each month. They have nice annual features like Technology Winners and Losers of 2012 or Dream Jobs 2012, in addition to themed issues each month. Computer Society has IEEE Computer magazine which is also very distinguished and I got a kick out of seeing articles by several of my professors. Computing Surveys is less often published, but it does a really great deep dive into topics sometimes at a key time when someone with a pivotal role will identify the issues between taking something shown in the lab into the world.
ACM is also very fine, and sponsors the Turing Award. SigGraph and other conferences and their many journals help transfer knowledge between technologists.
If you want direct community involvement, it is what you make it. In some places these groups are not as active as others. I was an officer in my local section of IEEE and it was time consuming, but worthwhile.
Both have practical benefits you can use like a discount for Safari for ACM, and a discount on Life and other kinds of insurance for IEEE. For most of us, fees do matter, so having a discount can make that a little easier.
Student chapters can be a good way to get started. In addition, I believe that IEEE has discounts for recent grads, as well as their GOLD (Graduates of the Last Decade) program. I particularly enjoyed affiliation with Eta Kappa Nu which was an independent engineering honor society for many years, but recently joined with and received sponsorship from IEEE. Eta Kappa Nu started at University of Illinois at Urbana-Champaign, and was a mostly a US thing. Recently they have started branching out internationally.
For people who are interested in networking outside their individual company, hearing monthly talks about the profession, and attending a low cost professional development seminar, at least where I live, IEEE fits the bill pretty well. ACM used to meet jointly with IEEE Computer Society where I live, but I thing that fell by the way at one point. If the local meetings are of high value to you, find out if your community has an active local chapter. If you are really ambitious, sometimes the mother ship will help you start one by providing member lists and typically some amount of funding for each meeting held in exchange for an attendance list.
IEEE has an organizational structure that I find regrettable, but it may be necessary. Local chapters are run through RAB - Regional Activities Board. In contrast, conferences are run by TAB - Technical Activities Board. Because of the split, many worthwhile conferences would come to town without any interaction with the chapters. This was unfortunate because the chapter newsletter was an inexpensive method of advertising, the local members needed the training from the conferences, the conferences needed the attendance from the local community, and at least a few times, enterprising officers in our chapter were able to find out about conferences and snag distinguished speakers for their monthly meetings without having to pay hotel and travel.
Great and Distinguished People, Mentoring Opportunities
The men and women I knew from ACM and IEEE were great mentors and leaders in technology. Joe Vickroy was our PACE Chairman and was involved in legislative advocacy for science and engineering after having had a career with NASA as a project manager on Apollo. Al Gross was our awards committee chairman, and a chief scientist at Orbital Sciences Corporation, and was the inventor of the Walkie-Talkie. Others had senior technical and management leadership at companies like Intel, Motorola, General Dynamics, Boeing, and local universities and colleges. We had people working with electric cars, alternative energy start ups, a consultants network, and educational outreach to elementary and high schools.
It Is Worth It
Getting involved with these organizations can be very valuable and satisfying, and what you put in will be rewarded back in terms of friendship, learning, and belonging to a community that stands for some worthy ideals.