Dealing with Knowledge Artifacts that are still in paper form
Fortunately, most journals are also available online, and articles can be copied for personal use. Before throwing out old journals I take a quick look for articles that might be of use in the future and I do a web search including the journal name and the article name. Articles in the ACM Portal or AAAI Digital Library (for example) can be copied locally for personal use by members after logging in. I used to keep journals, in paper form, almost forever but now having just high (possible) value articles stored on my local file system and indexed for search is good enough. I usually just save plain text, but if figures look especially useful I save them also.
Books are more of a problem. When we moved 7 years ago, I reduced the size of my technical library from about 400 books to about 150. Now when I purchase new books, I try to get rid of an equal number as gifts to my local library or sell them at a local used bookstore. A few times a year I go to reference a book that I have let go, but in general, I think that my technical library might be more useful with fewer books because I can find things very quickly.
Anyway, local storage works well for knowledge artifacts that other people create - usually storage and archival for personal use is allowed. For stuff that I produce (except for my published books that are owned by my publishers), I prefer public web storage.
I find that del.icio.us is a fantastic resource for organizing bookmarks for both knowledge artifacts on the web and for fun stuff that I might want to find again.
For fun stuff: I used to keep travel and family photographs on my KnowledgeBooks.com web site, but now I keep the best pictures on Flickr. I am tempted to start storing video clips (and I have some great stuff like dancers in India and Africa, etc.) on video.google.com when I have time.