Modern Postcard has a helpful page on U.S. postal increases that are to take effect May 14. Of special interest is how much more it's going to cost to send large "flats," like those that would contain a portfolio in a folder. It's not an across the board increase, but things that can't be sent through their automated system are getting assessed much higher fees.
Be aware of these changes and get your stuff in the mail now!
The Postal Service has a more comprehensive list, although the detail makes it very confusing to wade through. I intend to have a long talk with my friendly counter-help at the Golden Post Office to figure it all out.