One of the features lets you record macros for common tasks. Instead of repeatedly selecting the formatting for a cell or a group of cells, you can record the sequence of commands that perform the formatting and click on a button to use the macro.
Another feature, code-named "Sketchy", allows you to insert different drawings. Tony Ruscoe spotted some of the images that will be available in a library that resembles Microsoft Office's Clip Art.
Google Spreadsheets' code also references an option titled "Solver", which could be a tool for solving optimization problems, and an option to protect sheets and cell ranges.
Update: Tony points to a post from 2008 with more details about macros in Google Spreadsheets.