I needed to insert tables in wordpress posts, but I found just one plugin for this task WP-Table. But it will not work, it is not compatible with the new wordpress versions. What I did is to use google docs: File -> New Document -> Table -> Insert, populate your table.
Now, when you finished the table go to: Edit -> Edit HTML. Copy the HTML source code for the table and paste that html code in your wordpress posts, but in HTML EDIT MODE.
I hope that the method will work also for you.