i was wondering if i could make a flight controller using only an arduino uno.please help.
OK, I'll bite. A flight controller for what?
Absolutely. Multiwii is an open source flight controller software.
However, you will need sensors. Gyrometer, barometer, accelerometer, and magnetometer are pretty much mandatory. You can grab a 10DOF sensor that has all that for around $10 on eBay.
Ardupilot @ diydrones .com
I've never tried Ardupilot myself. However, you do need to download and install an older custom build of Arduino IDE to work with it from what I understand.
Multiwii will work fine with the current Arduino IDE.