The Google Analytics Forum is lighting up with questions about how to access the old version of Google Analytics. I linked to one thread, but there are plenty of threads with this question popping up.
The link is still there, but Google moved the link to the old interface all the way in the footer of the page. Google really wants you to switch to the new version of Google Analytics and by almost hiding the link, they think they can convert more people over to it.
Google Analytics event tweeted it:
To answer the most common question today: the old version of GA is still available in the footer (for now). We do recommend trying V5 :)— Google Analytics (@googleanalytics) April 18, 2012
So if you can't find it, scroll down.
Forum discussion at Google Analytics Forum.