Hello undisclosed:
A couple of qualifying questions could make your request for information a little bit more fruitful.
IE: How many cameras are you planning on implementing? 10? 50? 500?
Is it important that the client work in multiple operating system environments or do you only use Windows at present?
Are you trying to do complex things like Active Directory integration or just want basic recording whether continuous or on motion?
John's link will help you but some more detail on what your plans are will help you get feedback from other members.