The standard Arequipa [1] tours are the city tour and the countryside tour, both about three hours.
The city tour includes Yanahuara [2] church and lookout, the Compañía church, and the Santa Catalina Monastery [3]—ask for your guide to visit colonial homes [4] as well.
The country tour includes the mill at Sabandía [5] and the Mansión de Fundador [6].
The most reputable agency is Giardino Tours (Jerusalén 604-A, tel. 054/22-1345, www.giardinotours.com [7]), run by the same owners as La Casa de mi Abuela in Arequipa and La Casa de Mama Yacchi in Colca Canyon.
Another agency with a good reputation is Colonial Tours (Santa Catalina 106, tel. 054/28-6868, colonialtours02 [at] hotmail [dot] com).
A final option is Ricketts Turismo (Moral 229, tel. 054/22-2208, www.rickettsturismo.com [8]).
Links:
[1] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa
[2] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa/sights/yanahuara
[3] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa/sights/monasterio-de-santa-catalina
[4] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa/sights/colonial-mansions
[5] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa/sights/sabandia
[6] http://www.moon.com/destinations/peru/lake-titicaca-and-canyon-country/arequipa/sights/la-mansion-del-fundador
[7] http://www.giardinotours.com
[8] http://www.rickettsturismo.com