Namche Bazaar is one of the main stops on the trail up to Everest Base Camp, and is a great place to spend a day or two.
Acclimatization
If you have flown in to Lukla from Kathmandu, and walked to Namche in two days, you should spend at least a couple of days acclimatizing in Namche (or somewhere nearby at the same altitude).
View of Everest
The village is set in a horseshoe shaped bowl looking directly out at the sheer face of Kongde, and if you climb up to the viewpoint above the village, you will get your first view of Everest. You really feel as if you are deep in the mountains here.
Shops & facilities
Namche is the place to stock up on essentials - shops and stalls line the cobbled streets, and most of the traders are Sherpas or Tibetans. There are a large number of lodges; most of which are fairly simple, and numerous restaurants, cafes and even a couple of delicious bakeries. There is a post office, telephone facilities, internet, and a health and dental post here.
If you are in Namche on a Saturday, it is worth visiting the weekly market, where traders from Tibet sell their wares (often Chinese goods) in exchange for Nepali and Indian food and goods brought up from Lukla by lowland porters.