A couple of years ago I spent a few hours in Caldas da Rainha, because someone had asked me to buy pottery in a popular craft store there. It is a nice town, with pretty colored houses and a cobbled Old Town built on a hill. We went from Lisbon, it takes about 1 hour to get there. It is also near to Óbidos.
Seixal is amazing and has a lot to offer either if you decide to spend a weekend or a day there. You will always have coffee shops around, and the beautiful view to the Bay and Lisbon on the horizon. Is a cool and nice location for anyone that desires a weekend escape or wants to walk by the bay and do some sports.