I recently discovered that Stickies supports tables, even though there seems to be no menu interface for them. To access tables in Stickies, copy a portion of an Excel spreadsheet, TextEdit table, Pages table, etc., and paste it into Stickies. There you go, a table in Stickies. I haven't (yet?) found a way to create a table natively within Stickies, however.
You can change cell widths and heights by clicking on the dividers and dragging, as you'd expect. Perhaps a bit more surprising is that control-clicking within the table reveals an additional "Table" item at the top of the contextual menu. This contextual menu item opens the same "Table" palette that can be found in TextEdit (under the Format: Text: Table menu item).
[robg adds: I tested this in 10.3.9, and it doesn't work at all -- the pasted table just comes out as a single row of data. So my uneducated guess would be that table support is now native to the Cocoa text editing routines. Some apps, like TextEdit, contain an interface to the table code, while others like Stickies get the benefit of table handling, even without an interface. Perhaps someone with more technical knowledge than I could post a better explanation...]

