Zim: Your Own Personal Desktop Wiki
At a Glance
Take the power and flexibility of a wiki (like Wikipedia), wrap it with a friendly Windows installer, and make it run as a local application, no server needed. You've got Zim (free): a personal open-source wiki for managing your knowledge, tasks, and calendar. You can even get the portable version, put it on a USB stick or in a Dropbox folder, and take it with you on the go.
Zim supports familiar wiki syntax, such as using an asterisk to create bulleted lists (which are then continued automatically, like they are in Microsoft Word). You can surround text with double asterisks to make it bold, or with double slashes to make it italic. And because many of us are used to editing text in Microsoft Word and other WYSIWYG word processors, Zim also supports standard keyboard shortcuts like Ctrl-B for creating bold text, or Ctrl-I for italics.
Quick linking between pages is one of the core principles of the wiki context, and Zim doesn't disappoint. It supports the traditional Wiki link notation, which means you can surround a word or a phrase with double brackets to make them into a link (you will need to reload the page to see the link, but it's just one keystroke). Much like with bold and italic text, Zim provides a keyboard shortcut to make linking even more intuitive: Select some text and hit Ctrl-L. You can now link to that page, or even use the text as an anchor for linking to a different page (for example, maybe you want to link the word "apple" to a page called "diet"). It also supports CamelCase: When you meld two or more words LikeThis, they instantly become a link (no need to reload the page).
Despite the similar syntax, Zim feels very different from a browser-based wiki. For one, it is blazing fast in comparison: Everything happens instantly. Formatting is applied while you're still editing the page (no need to save or switch to View mode), links start working as soon as you type them in, and switching between pages takes no time at all. It feels just like a desktop application, because that's what it is. That doesn't mean Zim doesn't like the Web: If you want to, you can export your entire wiki as a collection of read-only webpages, with all links, styles, and images intact. In fact, the Zim website itself was written using Zim.
Another advantage of the desktop format is the Index: This is a sidebar on the left of the main editing area that shows your wiki pages as a long list. Pages can be nested using namespaces, so the Index sidebar can work as a tree. You could have all of your software-related pages taking up their own namespace, with page names like "software:Zim," "software:Excel," and use other namespaces on the same Zim wiki for documenting information that has nothing to do with software.
Zim also includes optional plug-ins, such as the Calendar plug-in that allows you to automatically create a page for any given date. Calendar pages are nested using namespaces, so that you have a main tree node for the year, another one for the month, and a final one for the day. In combination with Zim's ability to create to-do lists, this makes it very easy to use Zim as a traditional PIM.
If you are looking for an easy way to manage your knowledge and don't need to collaborate with others, Zim is a lovely and full-featured solution.