I use Chantecaille Loose Powder. Pricey, but it gives a soft, flawless finish, and doesn't "cake" after a few hours. The coverage is light if i apply with a brush, or heavy if i apply with a puff. It also doesn't make my face itch like other powders.
My second favorite powder is MAC Invisible Pro Set Powder. Love the finish, the color was true, but it made my face itch. My skin is strangely sensitive. I've heard it works well for other people, though.
I use Laura Mercier Powder Foundation for touchups during the day if my foundation has worn off in spots. I never cared for blot powder; i prefer blotting sheets.