The Beauty Closet, which carries RGB polishes, is having a 20% off sitewide (and they seem to have reasonable shipping rates too). Code: HAPPY2010. Expires: January 17th, 2010. Not a worthwhile code if you live in California and get slammed with CA taxes though (unless you buy more than three polishes).
BeautyBridge, which always offers free ground shipping on all orders and carries Lippmann, Nailtini, Sula, Pop and Pixi, is having an additional 10% off sitewide. Code: NEW10. Expires: January 18th, 2010.
CosmeticAmerica is offering an additional 9% off on Dior nail polishes. The Dior Vernis line goes for $18.85 normally, which is slightly cheaper than most department stores. Code: SHOPCA. Expires: January 19th, 2010.
And this isn't a coupon but CVS Beauty 360 carries Pop Nail Glam polishes for $10, instead of the usual $14.
...and before I forget, there will be an announcement about the banner design contest this Friday! Stay tuned! :D