I use a Mac application called DEVONthink. It allows me to import most document types, including PDF, and indexes them for rapid search. That's a big help for my Dragon Magazine collection, old BECMI D&D PDFs, etc. I can import pages from blogs with a quick bookmarklet. It can split up those file types, so for example I imported the Roleplaying Tips Weekly archives and split them into one file per tip, and organize them into subject areas.
It also lets me take notes in RTF format, and can automatically link terms to other documents like a Wiki. So I can be writing session notes and have character names automatically link to the character notes.
The coolest thing it offers is a limited AI text classification service. When I'm reading a document, it shows a pane for "See Also" where it suggests other documents that might be related. For example, I might be looking at a tip for speeding initiative in Rolemaster, and it suggested a few documents talking about initiative, some discussing other Rolemaster topics. And one for speeding up combat in general. Not all suggested articles are relevant, but it can be good for helping you make connections that you didn't think of.
This software has been good for keeping track of info as a GM, since the Wiki links and See Also let me find stuff fast. It also has a wicked-fast full text search function.
This is not a good piece of software for sharing information with your group. It's desktop software, and intended to be single user. Though there is a web sharing interface, it doesn't have the ability to keep some things hidden from the users while letting the GM see things.
Useful links:
http://www.enworld.org/forum/showthread.php?267864-campaign-software-what-do-you-use