Great resource pages from Physclips, covers pretty much everything you need to know about AC circuits…
All singing and dancing LRC applet.
You can control all basic values L, R, C , V0 [peak V] & f [omega].
The applet will display the voltage traces for resistor, inductor and capacitor, plus the current in the circuit. It also calculates the reactances and impedance [showing the vector sum as well] showing them as phasors for good measure.
All you need to know.
Simple applet showing Impedance v frequency for an LCR circuit.
Slider controls for R, L, C,& f