Samui's administrative and business centre doesn't offer a great deal to the short stay tourist. ATM's and postal facilities are now available in most other places on the island, but Nathon is the place to go for full banking services and the main Post Office, which also has a telecoms centre for overseas calls.
For anyone arriving by boat as a passenger, Nathon is also the island's main port (car ferries dock at Lipa Noi, a few kilometres south) and jumping off point for the islands of Koh Tao, Koh Phangan and mainland Surat Thani. To service the backpacker trade, a small cottage industry of sarong shops, bakeries, second hand bookshops, travel agents and internet cafes have sprung up along the waterfront.
Nathon is also the only place on Samui to find 'head' shops selling opium pipes, bongs, king size rizlas and all other manner of dope paraphernalia. Given the Thais increasingly hardline attitude towards drugs, it's wise to exercise caution with the use of any purchases.
The town's main tourist attraction for day trippers is its old wooden Chinese shophouses that line the middle road, selling an esoteric range of goods, including a lot of gold. Souvenirs bought here will also be considerably cheaper than elsewhere on the island. Food wise, any of the waterfront seafood restaurants are recommended for a taste of truly authentic and very spicy, local cuisine. Hotel accommodation is cheap and plentiful, but as few tourists have any need to stay the night, it's primarily aimed at the local market.