Yea, skip Reading Terminal. I was born and raised in Philadelphia and honestly, it's overhyped. Not only is it overly (Read as: unbearably) crowded, it's full of many eateries that have received numerous health code violations, many of which are straight ignorance.
I live in Center City and many residents avoid the market at all costs; instead, we hit up local farmers markets to support local farms and businesses.
The only thing worth traveling to Reading Terminal Market for are the donuts by Beiler's (The Amish; note: they are off Sunday and Monday).
Check out uwishunu.com! They have a weekly post (Usually posted on Thursdays) about what's happening in and around the city.
Also, this week, it's Wine Week!!! Lot's of events going on. Check out
http://phillywineweek.org/ for more info.
I live right by the Liberty Bell so maybe I am biased, but I'd say walk on Chestnut Street between 5th & 6th to take a peak. I mean, it is the Liberty Bell after all - haha!
What are you into? Local things? Touristy attractions? Dive Bars? Swanky Cocktail Lounges? I have quite a few recommendations!
If you enjoy a great cocktail and a swanky vibe, check out Hop Sing Laundromat (Cash only and you must be dressed appropriately: no sneakers, etc.).