Possibilities:
1) A wheel balance got knocked off and never was balanced correctly again (look to make sure you have only ONE weight per side of the wheel, two or more, means someone didn't align properly, if you have the normal stock rims; "koing" style rims will feature tape weights and it is okay to have more than one of those stuck on)
2) Indeed a bent rim is not easily taken care of to move to the back, it will still vibrate
3) Alignment may be out (yes certain aspects of an alignment can cause wheel shimmy)

I guess the question I need to ask is what kind of vibration do you feel? Is the steering wheel feeling like it is moving back and forth, do you feel like the ass end vibrating back and forth, is the ride bouncy (may indicate a blown shock)?

Look around your suspension parts as you said you where going to do and make sure there isn't like a filmy oily residue on your shocks, if there is you might have a blown shock on that side, but look at securely attached nuts and such, especailly near the ball joints.