Formatting data for output in a table can be a bit of a pain in R. The package formattable by Kun Ren and Kenton Russell provides some intuitive functions to create good looking tables for the R console or HTML quickly. The package home page demonstrates the functions with illustrative examples nicely.
There are a few points I really like: the functions accounting, currency, percent transform numbers into better human readable output cells can be highlighted by adding color information contextual icons can be added, e.