Since most of writers these days use online submissions almost exclusively--although there are still an awful lot of places that take only snail mail subs--it may have escaped your attention that postage rates went up on 4/17.
The main changes that affect us are the increase from 28 to 29 cents for a post card, and the increased increment (from 17cents to 20cents) for every ounce over the first one for both regular envelopes and flats. (The first ounce is still 44cents and 88cents, respectively).
New Postage Rates effective April 17
New Rates compared to Old