So I've missed World Book Day and GM's Day 2013, but at at least the DriveThru GM's Day Sale is still in progress (until 12th March inclusive). In the UK it's Mother's Day on Sunday as well - I've only just remembered to send a card, but mum isn't really interested in special offers on roleplaying games. Her loss! I'm keeping the dice.
Apart from DriveThru/OneBookShelf's Print program, the largest supplier of indie publisher RPGs rules and accessories in print is still Lulu.com (see the "Games" section for RPGs) Lulu are offering 20% reductions in March.
(This code is for the US site only)
Remember to shop responsibly and game with abandon! ;)