I usually take the T into the city, but unfortunately this weekend I'll be forced to take my car. Any suggestions on where to park at a (hopefully) reasonable rate would be GREATLY appreciated.

You have to specify where your going.  There's lots of places to park all over the city.

If your going to Quincy Market, try 75 State Street, $11.

Section of the city doesn't matter. I'll be all over the place ... Just wanna park as cheaply (and safely) as possible. Thanks very, very much for the suggestion

75 State is underground with security.  In addition to being close to Quincy Market, your within walking distance of Downtown Crossing, the North End and the Government Center T Station.