As a continuing service to the Chowhound community, here is my list of recommendable restaurants from my recent whirlwind visit to Beijing:
Xiao Wang Home Restaurant: has three (soon to be four) locations, all around Guanghua Road near Jianguomenwai. Very clean, very fresh dishes, though not terribly creative. Peking Duck has the crispest skin ever! The branch I visited is at Guanghua Dong Li #2, other locations at Yongan Xi Li #2, and Gongxi Dong Lu #4, Sanlitun.
Qiaojiangnan (Sichuan): also has several locations, including the Manhattan Building, the Intl Trade Building, and others. Outstanding Sichuan food, very spicy, extremely authentic. Try their 'shui zhu yu', slices of fish in a broth filled with chiles and Sichuan peppers, and their 'ma po tofu', which is excellent.
Hongmao Jiaozi (dumplings): on the third ring road at Guanghua Lu (near the Kerry Center). Excellent dumplings of all conceivable fillings. Not sure if they have an English menu, though you really cannot go wrong just pointing blindly (nothing on the menu would scare a timid Westerner). Very cheap (my order of two kinds of dumplings--12 per order, spicy cucumbers and a large bottle of beer was only RMB 18 (around $3).
Shunfeng Seafood (Cantonese): again, a multi-location place, including many locations in Guangdong province. The one I visited was on Jianguomenwai, near the Jianguo Hotel (as were all these restaurants, other than the Sichuan place). If you are craving abalone, shark fin, bird's nest, etc., this is the place. Also loads of fresh fish on display, which they bring to you before cooking it up. Beautifully prepared food, not too expensive (around RMB100/person).