Others have mentioned the Miracle on S 13th Street (East Passyunk area). Easy to get to via public transportation (bus or Broad Street Line) and lots of nearby places to grab a meal or drink while you're there.

Closer to Center City, Franklin Square has an hourly holiday light show.

In deep South Philly, Smedley Street just off Oregon - the whole block does decorations.

I recall one around 6th & League Streets (Bella Vista/Queen Village area) but I haven't been over there this month so not sure if they are still doing it.

City Hall has a lot going on including a ferris wheel, ice skating and the Christmas Village.

Enjoy!