Are you like me in that you have a million books, articles,and conference handouts...so many that you've forgotten what you have, much less where they are located? I've found an easy solution: LibraryThing.
LibraryThing can help you create an online catalog of your resources. It's really set-up for books only - and if you enter identifying info such as ISBN, etc., it'll autofill the details for you which is a real timesaver - but you can also manually enter and that's how I enter other resource types.
Now here's the best part: you can tag each entry by subject. By tagging, you can later do a search by tags to identify all your resources on that subject. So, you want to find all your books, articles, handouts on certification, just search by the certification tag.
You may need to be a little creative to get this to work best for you since the fields are fixed (and again, it's set up for books). For example, I'm using the Comments field to enter the location of the resource (where I have filed articles, for example).
By the way, you can share your books and tags with others on the site (similar to del.icio.us) so you can see what others like you are reading. I haven't used the social element of the site yet - instead, I've opted to just use it as a private catalog of my resources. I know there's software that could accomplish the same thing, but a benefit of an online catalog is that I can access it from anywhere - including at conferences when colleagues ask me for resource recommendations.