Grips
Many of these small cameras come with slippery plain fronts: no grip, nothing of texture to grip.
If you own an Olympus E-PM1 or E-PL3 or Nikon J1 or V1, I can recommend Richard Franiec's custom made grips. I've used several of his grips, including ones for previous models, and while they're a bit pricey (US$35 plus shipping), they are nicely tailored to the camera and well thought out. If you've got a different camera or don't mind a more generic grip, you can get the Flipbac grip for far less.
Olympus E-P3 users should consider getting the larger of the Olympus-made grips for the camera, and any of the E-P# users should go to eBay and do a search on "Olympus skin leather." The low-cost, pre-cut stick on skins you'll find come in a wide range of colors and textures, and I've found that they help you grip the camera, as otherwise the "skin" on these cameras is a slippery bare metal.
Nikon users should probably avoid Nikon's costly grips, as they add substantive weight and bulk to the camera for what's really a simple function. Flipback makes a low-cost model G4 grip that is suitable for the Nikon 1 cameras.
A different alternative to a grip is to put a skin leather on the camera. Aki-Asahi has such low-cost skins for the Nikon J1, all the Olympus Pens, Pentax Q, and several of the Panasonic m4/3 cameras, and will mail worldwide.