Quick entry. On Labor Day weekend, I spent at least half a day updating my Linked-In profile. (I also accidentally spammed everyone I'd ever emailed. Whoops, sorry.)
Tip: This was a good idea (update, not spam), and here's why.
I thought having an up-to-date profile would be prudent if any adcom googled me, but I didn't expect to get so much use out of my work. Today, I'm constantly viewing my own profile... to copy and paste information. Like yahoo, Linked-In has a profile of most companies, and from my public profile I can quickly dive into each one to get relevant information (size, industry, descriptions, etc). I also copy and paste my preloaded job descriptions, activities, etc. into fields. More or less, having an up to date linked-in profile is akin to having a professional cheat-sheet. So handy, and available everywhere - and beats a traditional resume due to the links.
Updating my profile also led to a number of other very significant events which completely consumed my labor day weekend (I did finish one monster essay, but no other progress). Frankly, had it not happened only 11 days ago I'd consider the experience grounds for a solid essay topic. That said, today I'm finding unlikely uses for linked-in, and loving it!
PS: The modern MBA applicant should be comfortable using two browsers; currently I'm leveraging Firefox and Chrome to pass information back and forth between schools as well. (Why does this matter? ApplyYourself, used by most of the top MBA programs, only lets you log into one school at a time. 2 browsers, 2 cookies, 2 schools.)