After the Lab Archive, I went on to build an online homework package (Timistry) specifically for chemistry problems, which I used in various forms from 2004-2008 at four colleges and universities I taught at, with a total of about 600 students. At the time, most of the other options were multiple choice.
How'd it work? A lot like Moodle calculated questions do now, although Timistry did significant figures correctly and more consistently than the version of Moodle that my institution uses today. (Chemists think that 6.00 mL and 6 mL are entirely different things.)
Worst bug: In an early version, students discovered that they could hit the 'back arrow' and try the same problem again, after getting it wrong.
Best feature: Did I mention significant figures? Sersiously. Super important to chemists.