There are various delicious recipes for ricotta cake, check out this thread
For cake making, I suggest ricotta di pecora, which is made with sheep milk, if at all possible. It is much richer and creamier than the ones made with cow milk. (If you never tried sheep milk, don't worry... first I was rather dubious about it, until I tried it!!)
If using regular ricotta with cow milk, mixing with mascarpone will give that rich creaminess it may lack.
I am not sure I would ever try cottage cheese for a cake though... too bland for my taste.