Not really the best-formed question, but I'm guessing you want to know the best places to park for free in Cambridge. You can find free - 2-hour parking at the end of many blocks around the city. You can also park cheaply ($1 for a couple hours) at the Porter Exchange Building lot in Porter Square. While shopping in Porter you can park for free in their shopping center parking lot. There is also free, 1-hour and 2-hour parking along Memorial Drive on the banks of the Charles River. As the previous poster says, parking is free at all meters in Cambridge on Sunday and after 6 or 8PM at night (read the meter for details).

yes, if you have a resident parking sticker! you can get one free from government center with proof of residency

Permit parking areas are free on Sundays in Cambridge.