Skating in fairmount park is great - especially down past the art museum, and boathouse row - really cool. I did it almost every weekend during one summer. You see a lot of great characters. Lots of people out with pets as well, if you'd like to bring rover along. There are a few vendors (sodas and pretzels etc,) who will set out water bowls for hot pooches.
One time I saw a man taking a beautiful red and yellow parrot out for a bike ride! He had the bird's cage strapped to the handlebars of his bike!
We would always park on the Franklin Parkway as close to the art museum as you can get. The trail runs right around the museum. You start skating right in front of ther museum winding around to the right past boathuose row, the waterworks and down along the river - it's very beatuiful. There's metered parking on the right hand side of the parkway as you approach the museum. There's a little oval parking lot directly in front of the museum, I think it's about $10 to park there.
It's also cool to take your skates off, walk up the "Rocky" steps, then there's a large flat area you can skate on right in front of the museum.
Another cool place to skate is the Schuykill river trail. Well paved and generally flat since it follows the river. It actually starts in Valley Forge National Park - but you can jump on just about anywhere along the trail.
here's a link for more info
http://www.montcopa.org/parks/schuylkillrivertrail.htm