If you like museums, I can recommend the following:
California State Railroad Museum
Sutter's Fort
Stanford Mansion
Governor's Mansion
Crocker Art Museum
A lot of people recommend Old Sacramento, and it is a popular tourist destination, but if you're looking for something a little more casual, I'd recommend hitting Midtown for shopping and dining (roughly J, K and L Street, between about 17th and 28th Street) and just walking about. The weather is just about perfect for strolling, there are a lot of trees and beautiful homes to enjoy in those neighborhood. And if you like historic homes, next Sunday is the annual SOCA Home Tour (
Sacramento Old City Association) that lets you visit restored Midtown historic homes, and there's also a street fair.