Via FilmakerIQ is Top 5 Easy Adobe After Effects Expressions by Sean Bowers, the first episode of a “Fix it in Post” series from NextWaveDV (embedded below).

For something comparable, My 5 Favorite Expressions by Harry Frank comes to mind, as does an Andrew Devis video Hidden Templates & Powerful Expressions. There's more on expressions in AE Help, the piled-on post Expressions & Scripting Resources for After Effects and others at AE Portal, and in various video tutorials at AEtuts+, for example a 5-part series by Frederik Steinmetz, Introduction To Writing Scripts For AE.