When Movable Type 4 came out, the author of the popular MT Blogroll plugin wrote a new plugin called LinkRoller, a.k.a. Link Roller. LinkRoller is a replacement for MT Blogroll--it's what you use in MT4 instead of MT Blogroll.
Unfortunately, it's hard to figure that out. I spent a while Googling for the new MT4 version of MT Blogroll before I discovered that the new link manager has a new name.
It's also hard to figure out how to install and set up the new link manager (which doesn't have as many features as the old one, but does what I want it to do). The installation documentation is decent if you're familiar with how all this stuff works, but not so good for beginners. There are a couple of usage examples down in the comments on that page, but also not great for beginners.
Someone named Justin posted a mostly excellent set of instructions for using LinkRoller in an MT4 widget; much appreciated. Unfortunately, the first example on that page uses tags that don't seem to exist, or at least that I can't get to work.
But the later examples work better; in particular, as far as I can tell, things work find if you use the standard MT4 asset tags, like mt:Assets, instead of tags like MTLinks.
As for adding links to LinkRoller, unfortunately there appears to be no bookmarklet to make that quick and easy, the way there was with MT Blogroll. The main LinkRoller plugin page (first link from this entry) has a video showing how to add a link from within your MT administration interface; it looks pretty quick and easy, but you do have to log in to MT first, which is a pain. Oh, well, better than nothing.
In case anyone's interested, here's the widget code I'm now using on my own main page:
<div class="widget-linkroll widget"> <h3 class="widget-header">Links of Interest</h3> <div class="widget-content"> <mt:Assets type="link" lastn="10"> <mt:AssetsHeader> <ul> </mt:AssetsHeader> <li><a href="<mt:AssetURL$>"><$mt:AssetLabel$></a><mt:If tag="AssetDescription">: <$mt:AssetDescription$></mt:If></li> <mt:AssetsFooter> </ul> </mt:AssetsFooter> </mt:Assets> </div> </div>
Mostly, I'm posting this entry in order to try to build a stronger link in search engines between MT Blogroll and LinkRoller, in hopes that people who search for the former for use in MT4 will be able to more easily find the latter.