We're big fans of web-based software around these parts, as we've mentioned a few times before. Unfortunately, web apps often have rather poor documentation, particularly for the more advanced functionality. Luckily, online forums and blogs often do a great job of filling in the documentation gaps.
Web Apps - Stack Exchange is a new question and answer site from the makers of Stack Overflow. It bills itself as a "free, community driven Q&A for power users of web applications." While the site is definitely geared towards more advanced questions, don't let the "power users" line scare you off. There's plenty to be gained from the site just by browsing, and there seem to be a range of questions for the time being.
The basic idea behind the site is that anyone can ask a question (related to web applications) and have it posted on the site. Other contributors can provide answers to the question, and both questions and answers can be voted for or against by the community. When you ask a question, you also get to choose the response that best answers it. The key to any such service is the quality of the community, and Stack Overflow has a very good reputation.
The site encourages questions that have clear, correct answers like "how to run multiple Dropbox accounts on the same PC," but there are also a number of recommendation questions along the lines of "what is the best web-based project management app?" Even if you're not ready to ask a question, it's worth looking around the existing questions a bit to learn some new things, and to help out if you can.
There are certainly plenty of questions related to web apps that aren't business related, but every post is tagged, making it easy to find relevant questions and answers. Some interesting tags to browse through include web app recommendations, time tracking software, inventory management software, blogging (and wordpress in particular), Google apps, Google analytics, security, hidden features, and plenty more.
Anyway, if you've got some time on your hands, or a burning question about a web application, it's definitely worth heading over to webapps.stackexchange.com and checking things out. Of course, if you've got any questions related to business software in general, or about Web Apps - Stack Exchange itself, the comments await.