[Updated in 2008: It turns out that I was wrong about how Forever Stamps work. I apologize for the misinformation. For updated/correct information, see my new entry. Leaving this entry intact for historical purposes, but don't believe anything that I wrote below about the Forever Stamps.]
For anyone who missed it: US postal rates have just gone up. The first ounce for a first-class letter now costs 41¢; other rates now depend as much on the size and shape of what you're mailing as on the number of ounces, primarily (I gather) because they want to encourage people to send mail that can be processed automatically rather than mail that needs to be processed by hand.
Most especially, writers and editors should take careful note of the fact that a manuscript-size manila envelope now costs 80¢ for the first ounce, and 17¢ for each ounce after that. A single first-class stamp is no longer sufficient for mailing a one-ounce manuscript.
Which is too bad, because the USPS has also introduced (last month, I think) a new kind of first-class stamp called the Forever stamp that will be good for mailing a one-ounce first-class letter (in a #10 envelope, not a bigger envelope) forever. When I first heard about this, I had figured that when this stamp came out, I would buy hundreds of them and would never need to buy stamps again; but in fact as far as I can tell there's no need to stockpile them yet, because the plan is to keep producing them. So when the next rate hike is announced, before it actually happens, you can buy a bunch of Forever stamps. The USPS's expectation is that people will buy Forever stamps at that point to ease the transition to the new rate (we all should've done this last week), so nobody will have to buy a bunch of 1¢ and 2¢ stamps to cover the difference between old rate and new rate; but of course you can also buy a whole bunch of Forever stamps to avoid having to deal with the next several rate increases.
But again, the Forever stamp appears to be good only for the first ounce of a first-class letter. I send so few of those these days (usually paying occasional paper bills) that I'm not sure it's worth it to me to buy a bunch of those stamps at this point. (I'm not sure whether you can use a Forever stamp for the first n¢ of postage on a non-first-class piece of mail.)