Hi, best and affordable way to reach pondicherry is by taking a bus. Plenty of state buses are there from CMBT bus terminus. It will cost you around 170-180 bucks only. You can also hire a taxi, but will cost you much more around 2000 rupees. Hope it helps you and do share your experience on Tripoto.
Bus Ride from Chennai to Pondicherry is actually cheap.
Both the govt. (PY and TN) operates bus at a frequency of a bus every 15 minutes. An ordinary bus will be costing around 90-100 Rs.
A Deluxe bus will cost around 100-120 Rs.
A Volvo A/C bus will be costing around 190-240 Rs. If u want ultra-sophistication, u could very well get in a private carrier which provides multi-axle A/C buses. It will be costing around Rs. 300. Good Luck!!
I recently visited Pondi. You can book Orange Bus from Chennai, you will reach in 2-3 hours. Plus the buses are pocket friendly and very comfortable, they have AC and sleeper seats, plus they will give you water and snacks.