Sheetmetal Mike

There various options. One is an exterior grade anti-skid paint. You can buy it from Home Depot:

http://www.homedepot.com/buy/sure-step-1-gal-acrylic-gray-pearl-anti-slip-concrete-coating-su-0308.html

It's a good idea to seal the concrete.... Concrete sealer is available at the local Lowes or Home Depot....Just add the grit they sell for just this purpose...or you can just etch the concrete....I personally would etch it first then use a stain sealer with grit...

http://www.concretenetwork.com/products-sealer/

http://www.sealkrete.com/acid_etching_no_cne.htm

You can etch it with acid or sand blast it.
Concrete Etching TipsH&C Concrete - Products - H&C® Etching Solution

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You will have to roughen the surface before applying any non-skid product anyway, so you could just rent a floor grinder, and skip putting on the coating.

http://www.youtube.com/watch?v=5_Nch4v7LOQ

you could have it scarified. in thisprocess small steel "shot" is shot at high pressur at the surface of the concrete.