Budget

A convenient place for finding reasonably priced food is the food court of the Conjunto Nacional mall (also see Buy, above). The mall is located right beside the main bus terminal (rodoviaria) and at walking distance from many hotels and of the main attractions such as the Three Powers Square.
SCLS 201. Right beside Banco Central's main building, this street is packed with cheap self-service restaurants and a few ranging from mid-range to splurge.
Local chain Giraffas (several locations around town) rivals McDonalds in the fast food market by serving sandwiches and cheap beef/chicken + rice-and-beans set meals.
Pizzaria Dom Bosco. The oldest active pizzeria in Brasilia. Sells reasonably cheap pizza by the slice. R$ 1.50/slice. 

CLS 107 Bloco D Loja 20, ? (+55 61) 3443-7579. M-Su 8AM-11PM.
CLN 306 Bloco C Loja 46, ? (+55 61) 3347-0904. M-Su 9AM-11PM.
CLSW 303 Bloco A Loja 18, ? (+55 61) 3341-2493. M-Su 9AM-11PM.

Mid-range

Don Durica - SCLN 201, Bloco A, (61) 3326-1045. (Mo-Sat 11:30am-3pm/6pm-midnight). This all-you-can-eat buffet offers more than 50 dishes for lunch, mainly from Minas Gerais cuisine.
Vegetarians may try and escape ubiquitous meat dishes of Brazilian cuisine at Bardana - SCLS 405 bloco A, (61) 3242-3532. Try the tropical juices too.
El Paso Texas, SCLS 404 - Bloco C , lj 19, ? 3323-4618. A favorite with American expats and locals alike. Besides the Tex-Mex dishes, try the great frozen margaritas and whatnot. On its street there are also several other restaurants to choose from. R$ 20-40.

Splurge

Fogo de Chão - SHS quadra 5, Bloco E. Tel. +55 61 3322-4666. Traditional brazilian steakhouse. It features an all-you-can eat salad buffet, imported cheese, brazilian side dishes and 15 kind of cuts of fire roasted meats that are brought to your table almost non-stop. Service is top-notch. R$ 79,00/person. Opens mon-fri 12h til 16h (lunch) and 18h til 0h (dinner), sat-sun 12h-0h (non-stop).
Patu Anu, Setor de Mansões do Lago Norte - ML trecho 12, Conjunto 1, casa 07., ? 3369-2788 (patuanu@aol.com). Tu-Sat 08:30 to 02:30, Sun 13:30 to 18:00.. A hideout at the distant Lago Norte zone that serves creative dishes that mix international recipes and national ingredients such as jacaré (alligator), Brazil nuts, tropical cherry cokes etc. Booking recommended. Main dishes from R$ 40.  edit
Villa Tevere, CLS 115 Bl. A, ? 3345-5513. Mo-Sat 12-15:00 and 19:30-1:00. Su 12-17:00. Cosy Italian restaurant with good wines and quiet live Brazilian music on the poop deck  edit
Zuu aZdZ - CLS 210 - (61) 3244-1039 - Tue-Fri 12-15:00 and 20:00-00:00. Sat 20:00-00:00. Contemporary, cosmopolitan cuisine. The architecture of the restaurant is itself an attraction. Main dishes from R$ 60 to 180. Beverages cost three to four times their normal prices. Wine prices range from R$ 60 to R$ 10,000.
Aquavit Setor de Mansões Lago Norte - ML12 conjunto 1 casa 5 - (61) 3369-2301. Open for dinner only, Thu-Sat. Run by Danish national Simon Cederholm, this restaurant offers a six-course meal, which changes every month. Inspired by Scandinavian cuisine, the place is popular with Nordic visitors to Brasilia. Reservations are a must.