Wolfram Alpha can be thought of as a super calculator. This calculator has the ability to understand fairly complex questions such as “What is the population density of Chicago?” and also college level math problems such as integration, limits, and 2D & 3D plotting. While tools such as Matlab or Mathematica can be more powerful, Wolfram Alpha is a handy free tool. Interesting fact: Wolfram Alpha powers some of Apple’s responses in Siri.
Owned by Altium, Octopart is a tool that searches “over 200” distributors for their price and stock of 30 million components. Octopart is a great tool for anyone who is looking for the best price or a hard-to-find component.
If you assume Reddit is just for snarkery and memes, you haven't really delved in. There are several great sub-reddits for EEs and the main one dedicated to electrical and computer engineering has about 27k subscribers from all walks of life who are great at answering any question you may have. Plus, it's good to check in periodically and get ideas. Also check out their EE books section.
Upverter is a cloud based circuit board design tool (aka EDA). Upverter can assist with developing schematics, PCB layouts, bills of materials, and gerber files. Aside from being cloud based, Upverter also prides themselves on having a low learning curve. Give the free version a try and see if it will work for your application! If you're looking for a free software take a look at our article on the topic.
This is the site for the "world's largest professional association for the advancement of technology." Odds are you already know about it, but if you don't, you should join immediately. Membership gets you access to a massive EE community, tons of resources, discounts, and useful publications and standards. Absolutely vital for any engineer.
Adafruit provides a good bit of documentations for a lot of their products, various projects and topics. While these articles tend to geared to beginners and hobbyists, it provides a good resource to discover a new topic. On a similar note, Sparkfun Electronics have their own learning prortal.
Stack Exchange offers over 130 “Q&A Communities”, one of which is geared towards electronics. Users are able to post questions and get them answered by other members.
Dave, the founder, is an electrical engineer who posts videos on various engineering topics. With an Australian accent and a sense of humor, Dave's videos are always interesting to watch. In addition to his, videos he also has a message board on his website.
Coursera searches colleges for free courses, since many colleges are offering classes online. While you most likely won’t get credit for these, the "student" might learn a thing or two in the process. Two (of many) colleges that offer some courses for free are MIT and Stanford.
Circuit lab offers a cloud based SPICE analysis tool. While it’s not free, it does discounts for students and lower-cost plans for hobbiest. Ciricutlab won’t replace your Orcad or Altium package, but does give the user a low cost option for easy to use analysis. Take a look at the demo they have posted.
This free cloud-based simulation tool lets you test your analog, digital, mixed-signal, and mechatronic systems. SystemVision has a ton of ready-made designs and a community to help address any problems you may be having with your circuits.
Hackaday is like the punk rock version of Adafruit, with tons of cool hacks and tips and even their own io. It's a fun site for EE's to get ideas and expand their creativity, even if it tends to cater more to the tinkering crowd.
So there's a list of our favorites, but if you have any other suggestions, feel free to suggest them in the comments section.