Quoting Yurvette [♥]:" thats the thing I havent dyed it in about 6 months... or something like that. lol. "
Unfortunately it's probably not going to get much lighter unless you wait until summer, when you're out in the sun and going swimming and all that. But be warned - it is likely to fade into an ugly reddish color.
If you don't want to wait and your ends and roots aren't drastically different[like light blonde roots and black ends] then you can go and get it highlighted and just let that grow out.
If there is a huge difference you'll have to bleach the dark parts and tone them.