2008 was the year of the brunette. Many of the designers and magazines were showing models that were a rich espresso brown. 2009 will still be a year with the rich hues, but I think the color will be a little softer, more milk chocolate with some subtle highlights. Think Miranda Kerr. The beautiful Australian model dating (and rumored to be engaged to) Orlando Bloom.
Now don't get crazy and run out and buy chocolate brown hair color, you might just end up looking like a stale chocolate bar. But take a look at your eye and skin color. If you have blue eyes and milky skin you'll look great with the rich color, just be careful to not go to dark (Courtney Cox). Courtney is beautiful, but sometimes looks a little harsh with the dark hair. Lightening a couple of shades will soften up any wrinkles you might have and make you look younger.
If you have brown eyes, go a shade or two lighter or darker than your eye color. If you're adding highlights keep them BLENDED! There's nothing worse than seeing a girl with dark hair and yellow strands of hay sticking out. My colorist says, "it looks like a bird has pooped on her head."
For you blondes don't frete. You never go out of style, but my advice to you is the same for the brunettes, BLEND, BLEND, BLEND. Add a couple of different colors to add dimension to your hair. Good Luck and have fun with it, you can always dye it back if you hate it. You never know, you might land your own Orlando Bloom.