Singulars vs. plurals in column names.
Jeff Atwood has a good post about database design: Maybe Normalizing Isn’t Normal, all about data normalization. I like the quip it ends with: normalize until it hurts, denormalize until it works.
In the comments, a few people quibble with the naming of his tables and columns. It’s an age-old debate: are relational database tables named with a singular or a plural? The original proponents of relational design used singular nouns: User, Employee, Manager. But conceptually, a table is a set of things, and so should be plural, no?