City Bicycle Works rents hybrids and mtbs for $20/day.
2419 K st.
http://citybicycleworks.com/

Bicycles Plus in Folsom rents all kinds of bikes
705 Gold Lake Dr,
Folsom, CA 95630
http://onlinecycling.com/page.cfm?pageID=78
This shop is located right off the American River Bike Trail.