I’ll bring printouts to class tomorrow, but if you’d like to get a head start, here’s a link to the opinions in Weinberger v. Wiesenfeld. The Syllabus tab is what you’ll see by default (right under the case title). Click on the Case link next to it, and you’ll see what you need. Both concurring opinions (which are very short) are on the same page.
You may also find it helpful to read the American Bar Association’s “How to Read a U.S. Supreme Court Opinion.”
Also, as a followup: the name of the case I was trying to remember in class yesterday is United States v. Windsor. If you follow that link, you’ll see that Oyez.org has sidebar links to the various opinions, as well as general information about the case (so I wasn’t completely crazy in thinking that I should have been able to see those links yesterday; I think they’re missing because Wiesenfeld is an older case). You’ll also see that my memory was faulty; the Justices did split along the typical ideological lines in Windsor.