It may depend where you are but over here "VFR over the top" is quite legal. You just have to maintain cloud, traffic and terrain clearances.
The US is very flexible, and you can fly portions of IFR under VFR but remaining on the clearance. For example, departing under an IFR FP which may take you one a big SID all over the place - if it is VFR conditions you can request say a "VFR climb en-route" - basically bypass the SID and climb VFR subject to ATC approval of course and remain on the IFR clearance.
They also have the "IFR to VFR on top" clearance which is a useful clearance to climb through the cloud. Once on top, you cancel IFR and continue VFR. If not on top, you continue IFR or whatever you decide to do (shoot the approach back home for example).
Great system
[edit: you need an IR of course
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