A quick and easy way to store things. It is visual, so a great way to quickly check back and remember things. I tend to use it as a storehouse of re-usable material (eg collecting Creative Commons images), but you can also present your work on here, or use it to archive research material.
Store all those articles and webpages you have read or want to read. Diigo is a bookmarking site, you can also create a group and have multiple people post to it. My only problem is that it just adds to your workload, so to make life easier I suggest pulling out a quote from the article you are bookmarking that got your attention, or adding your comment after reading it, and why you thought it worthy of bookmarking.
I like the way this tool searches social networking sites, news, and blogs for you. I can get a quick snapshot of activity in a very short space of time. It does feel a bit incomplete though, and there must be lots missing. Why not go a step further with NetVibes and get it to write an article or summary for you? Ask it to aggregate all content on, say, "edcmooc" from the past 6 months and produce an article, infographic, and series of questions all gleaned from this content. Press "reminx" and it will do the same thing, but come up with different results.