Wow, what a great thread.
For Mexican, we like Mi Pueblo at 800 N. Petaluma Blvd., Petaluma ($$).
For Chinese, we like Hunan Village at 295 N. McDowell Blvd., Petaluma ($$).
For Indian, we have only one choice (unfortunately) but it is a decent one (fortunately) if a little expensive for its calibre (unfortunately). Star of India at 295 N. McDowell Blvd., Petaluma, next door to Hunan Village in fact ($$$).
For eclectic, try Cafe Zazzle at 121 Kentucky Street. They serve reasonably priced, high quality, fusion dishes. Think asian-Mexican-southern US-etc., over the top fusion ($$).
For more shi-shi a couple of high end Italian restaurants come to mind: Cafe Giostra at 1390 N. McDowell Blvd. #L ($$$) and Cucina Paradiso, who even have a website http://www.cucinaparadisopetaluma.com/
If Italian isn't your thing, but you still want shi-shi, Deschmire's (which recently changed hands) remains a reliable standby. Deschmire's is a continental-French-ish place located at 304 Bodega Ave., Petaluma ($$$$).
If you prefer more modern California cuisine, try Central Market at 42 N. Petaluma Blvd., Petaluma (http://www.centralmarketpetaluma.com/;
Now the lamentation - Petaluma has no truly good pizza restaurants! I'm not a deep dish kinda guy, so Old Chicago Pizza need not apply. Mary's Pizza Shack is limp, damp and oily. Likewise New Yorker tends to be limp and a little soggy. Giacomo's makes an "okay" pie, but it doesn't have much competition. In fact, Round Table stacks up pretty well compared to most of Petaluma's mom & pop pizza joints. If you know of any in or near Petaluma, please, please, please...share!