Yeast Starter

I made a 2L yeast starter last night and about 2hrs later I noticed it had already produced some sediment. Is this normal activity for yeast starters? I plan to brew this weekend so should I just leave the starter sitting at room temp or should I refrigerate it until brew day?

Might the sediment be trub that settled out?

I'm not sure. So how do I know if the yeast have been active?

What yeast did you use in the starter?
If it was Wyeast or White Labs, or similar, then the timing sounds good. If you are starting from a very small amount of yeast (as from a naturally conditioned bottle), you may want to put off the brew for a week or so.
You can see if the yeast is active by swirling the starter. It is a good idea to do this every hour or so (or whenever you think of it). If the yeast is active, it will release some CO2. The other way is to keep checking on the amount of sediment. If the yeast is active, the sediment (yeast) will grow.

-a.

its normal. let it go till the night before your brew then stick it in the fridge. then gently pour off most of the wort. then when it comes time swirl it around and pour it in.

I made a 2L starter for a beer with an O.G. of 1.066. Will this be enough of a starter?

According to the Mr. Malty calculator, as long as you've been giving the starter a shake every once in a while you should be fine. http://www.mrmalty.com/calc/calc.html