The rate increase for US mail is only about a month away. Here is a link to the Postal Bulletin that has all the new rates.

Note that first class letters under 1 oz will now be 39 cents rather than 37 cents.

Also note, that the surcharge for "thick envelopes under an ounce" which often applies to the bubble envlopes that ship a chip goes to 13 cents, making postage for these 52 cents

The charge for each additional ounce goes from 23 cents to 24 cents, so none of your old 23's will be enough. Better stock up on some penny stamps [g].

Priority Mail now starts at $4.05 rather than $3.85.

You may want to print out the "Ratefold" from this site for reference. You are supposed to be able to get these from your local post office, but it was several weeks after the last increase before they were available here in Oregon. Note that it's 16 pages if you print them all.