Um, I don't know that this is really shopping but I really have to recommend to any TSF'er traveling in Beijing and anyone that loves clothing and textiles visit the Ethnic Costumes Museums. It's a little difficult to find if you don't know what to look for. It's situated on the campus of the Beijing Institute of Clothing Technology. You have enter the campus and walk through it and go up to the third floor of one of the buildings.
It is one of the nicest museums I've ever seen in Beijing (that's saying a lot). Everything was well preserved, displayed and lighted. There's almost no people in it. It's basically a very nice collection of clothing from various ethnic groups in China (mostly Han which has it's own room and a lot of amazing Miao jewellry in another, lots of beautiful batik work from Guizhou area). I can't recommend it enough for visitors. Across the street is also a few small stores selling big glossy fashion magazines as well (I assume for the students). There's an entire suit made from fish skins, as well as gorgeous Art Deco period clothing in the Han room with a Chinese twist and loads of painted silk purses in the museums which are must-sees.
As for shopping I was really unimpressed. There's not that much there that isn't mass produced and of not terribly good quality. I would say head to Geng Xiang near Beixinqiao and pick up some organic tea (chrysanthemum, jasmine green tea, and tie guanyin). Pick up an Yixing tea pot and cups at the Maliandao tea market building and some tea implements like bamboo scoops. You can also check out the puerh tea there but I'm no puerh aficionado like some people are. On the second floor is a tea store with higher prices but they do have "tea liqueur" for only about 150 RMB. A novelty liqueur that seemed kind of interesting.
I also would recommend going to pick up fabric there; things like shantung silk if you have the money and then going to a seamstress/tailor shop to have it made into pillowcases and duvet covers or blankets. For the students, I found several "traditional" patterns like the dragons and phoenixes with peonies on cotton and had those made into throw pillow covers as gifts. I think I paid between 12-20 rmb depending on the size of the pillow each. I guess the traditional fabric would have a red background but I found blue, green, black and white as well. I think it might be a bit hokey looking in China (I had a conversation in the fabric store with a young Chinese guy where he asked me, "Foreigners...they actually like this kind of pattern?" I think he was implying it was not 'cool' haha). I think it's cool.
I didn't really like Panjiayuan. It's crazy crowded with tourists and to be honest most of the stuff their is just cheap crap. You're not going to unearth any antiques in Beijing, so come here if you want to pick up Mao clocks and posters.
A lot of the clothing in the clothing markets is TINY. I'm serious. I was like an XXL there and couldn't fit into most of the short and trousers because of my hips there. I would say pick up some nice cotton tees from places like Wudaokou clothing market. Jeans too if you squeeze into them. Don't be afraid to pick up and look through mens clothing if you're a woman either. The guys sizing might fit you better (longer and also wider/bigger sizes). The mens clothing has a lot of cool tees, big sweaters. Also mens wifebeater tanks fit me while women's didn't. I picked up from one of the markets men's "undershirt tanks" made of drapey modal/viscose there.
I also recommend Rouge Baiser in Sanlitun. This is the place to come for nice children's gifts; baptism and baby gifts. Embroidered pillows, sheets etc. I bought a really nice pj set for a child that is slightly mao suit inspired. The children's clothing is Asian inspired and adorable yet classic. They also have cashmere robes and linen and silk pjs for adults. It's pricey for China but if you convert into foreign currency what you're paying and take into consideration the fabric you're getting a better deal than you would at home.
Lost & Found is another cute store. They have tons of those glass vacuum thermos in many sizes and patterns that you see everywhere in China. Lots of mugs and knick knacks. I like the tees and mugs that have two little Chinese children on them. They also have a small but interesting selection of art books (though go to Timezone 8 and 798 to get a better selection). They also have sales at Lost & Found.
Hope this helps someone. When in doubt, check The Beijinger or CityWeekend and use The Insider's Guide to Beijing for more current recs.