Locally they offer Internet Pro Plus with HBO, and Internet Pro Plus with Showtime. Both packages include the premium channel along with Digital Economy, Streampix, and Performance Pro Internet. If the same holds true for your area Comcast may have the Digital Economy channel lineup online at https://www.xfinity.com/learn/channel-lineup, or they may have included it with one of your recent bills. Check https://customer.xfinity.com/.
Service Centers and Xfinity Stores should have printed channel lineups. Check locations and hours at http://www.xfinity.com/support/service-center-locations/ to pick one up, or call Customer Service at 1-800-Comcast and have them send a lineup to you.
A typical Digital Economy lineup includes: Limited Basic/local channels, A&E, AMC, Animal Planet, BET, Cartoon Network, C-SPAN, CNN, Comedy Central, Discovery, Disney, E!, Food Network, Fox News, Hallmark, History, Lifetime, On Demand, truTV, TV Land, USA, The Weather Channel, and Music Choice.
That's for zip code 17401 in Central PA. Other areas should be similar, plus or minus a few channels.