Missing Wikipedia articles
Some missing topics from my collection of graph algorithms articles:


Dynamic graph algorithms
K shortest paths
Spanners and approximate shortest path data structures


Also, not so much missing topics, but a lot of the articles on topics covered by undergraduate algorithms classes kind of look like they were written by students in those classes. There's a deeper level of understanding missing, and they take a dogmatic point of view that reflects a single textbook rather than a synthesis of multiple sources. More expert help there could be useful.