Wish I could be in NYC in May for this: National Stationery Show
If you are near a FLAX art & design store, run, don't walk there now to get some goodies. Pens, paper, journals, you name it.
Learn about the history of mail, via the National Postal Museum. Visit if you're in DC.
Good article: The Found Art of Thank-You Notes - NYTimes.com
eggpress is on board with National Letter Writing Month with their #write_on campaign. See if you can get in for a set of free notecards to start!
I have loved getting OliveBox so far, a monthly subscription service for paper lovers. Very cute stuff!