|OS X (UK) |Unicode|Alt Code|HTML (Name) |HTML (Number)
------------|------------------------------------------|-------|--------|------------|------------- Upper case Ç|⌥ + ⇧ + c|U+00C7 |Alt 0199|Ç |Ç Lower case ç|⌥ + c |U+00E7 |Alt 0231|ç |ç
More info @ Wikipedia.
Bit.ly alias: bit.ly/c-cedilla
On Mac I just hold down the c key for a second and hit 1.