The city of Koszalin services as the commercial hub for the the towns to the South and much of Poland’s Baltic Coast.
The small towns in Northern Poland live off farming and summer tourists. They are generally served only by small shops. Koszalin provides those services and goods that are distributed on a larger scale.
There are major markets, shopping centers and building supplies as well as banks, computer services and a transportation hub. There is rail into Koszalin from which you can go on to the Baltic beach town of Darlowo.
Driving from Warsaw to Koszalin is somewhat tedious in that most of the way you must use two lane roads. it takes about 8 hours to make the trip. The roads, as of the writing of this information in July, 2009 are being widened.
But as you make the trip you will go through many small towns. They have speed limits of 40 and 50 km/hr. And they enforce them with photo radar. So it is very important that you watch the road for the black congested area signs.
Some people avoid this by taking an alternate route through Gdansk. The trip is about 100 km longer but the roads are wider and faster. You avoid the small towns.
Here is a map. To get directions on how to get there from Warsaw, or any other location for that matter, use the get directions link.