You don't menton which station in CT you are near, but in any event unless you are travelling same day r/t on a Sunday-- I think most park and ride parking lots charge. As for getting from CT to EWR. Take Metro North to Grand Central, then the S-Shuttle to Times Square (1 stop), then the #2 or 3 Downtown 1 stop to 34th St/Penn Station where if you're really looking to save money, you'll buy an off peak (assuming that's when you're travelling) r/t ($8.50) on NJ Transit NY Penn to Elizabeth. Get off at the AirTran stop (the one between Newark Penn and Elizabeth) and buy a $5.50 o/w ticket on the monorail to the airport (If you buy a NY-Airtran ticket that includes the monorail to the terminal it is $14 o/w).

So a total of $23.50 round trip + whatever your CT costs are.