Thanks abhishek and diaz,
working with 555 is fine( i have done this before),but the problem is generating different freq is little difficult with it.
so i would appreciate if some one help me with some IC which has IIC interface, or any other suitable interface, so that i can send some count corresponding to frequency and forget it. If i want to change the frequency then i will send some other count and forget.
Do we have any such IC's available, if so please let me know.

Thanking you very much in advance.
-sathish