Caltech has agreements with these hotels and you can get special rates described here.

The Athenaeum

551 S Hill Ave, Pasadena, CA (On campus)
626 395-8200
The Athenaeum

The Saga

1633 E Colorado Blvd, Pasadena, CA (0.5 mile to campus)
(626) 795-0431
The Saga Motel

The Hilton Pasadena

168 S Los Robles Ave, Pasadena, CA (0.8 miles to campus)
The Hilton Pasadena

The Sheraton Pasadena

303E. Cordova St, Pasadena CA (1 mile to campus)
The Sheraton

The Courtyard by Marriott

180 N Fair Oaks Ave, Pasadena, CA (2 miles to campus)
The Courtyard

The Langham Huntington Hotel & Spa

(formerly The Ritz Carlton)
1401 South Oak Knoll Ave., Pasadena, CA 91106 (2.5 miles to campus)
(626) 568-390
The Langham

Lewis Research Group, Division of Chemistry and Chemical Engineering
Caltech 127-72, 1200 East California Boulevard, Pasadena, California 91125