I've had the most success with Tall Girl. I know they're owned by Long Tall Sally now, and I haven't bought anything from LTS yet, but it looks like little has changed from what was in Tall Girl stores so I'm hoping it's good.
I bought all my dress pants at Tall Girl, and they fit well and have held up well. I also bought a couple of blazers there. The fit was a little weird, since I have wide shoulders and tiny boobs, so that, combined with the fact that my workplace is uber casual, means I don't wear them much. I definitely need to find a tailor, though, because they're nice. I also bought all my sweatpants and workout gear there during my track and field years (and am still wearing the sweatpants to lounge in and go to the occasional yoga class).
Overall, some of their stuff was pricey but there were also good sales. LTS looks to be the same, so here's hoping.
There are a large handful of catalogs and sites catering to tall women's clothing that I watch, but some that I've tried have a weird fit or iffy quality (I'm looking at you Long Elegant Legs). I would suggest ordering one thing from a new company to see if you like it before purchasing a whole new wardrobe.
Shoes are a big one too. When I first took to the internet looking for large size women's shoes, I was about 13 and my mom was sitting right next to me. We promptly entered the wonderful world of 5-inch clear plastic stilleto platforms and thigh-high pleather boots. Drag queens can rock that sh#@, but it's not really my style. Thankfully, we've come a long way in only 10 years or so and there are tons of sites devoted to large size shoes for the ladies. I used to buy most of my dress shoes at www.designershoes.com, but lately their selection has been boring. **Actually, I just checked it and most of their stuff is Barefoot Tess anyway.** Barefoot Tess is great when it comes to catering to the tall ladies. I wear a 14, and they have more styles and cute options than I've found anywhere else. Their shipping costs are ridiculous, but I still order from them. (See those Jeffrey Campbell heels down a few posts? Totally bought them this summer. A-maz-ing.)
Specialty shopping is easy and you're likely to be disappointed when you find the perfect item in a department store only to realize it's too short. But honestly most of my clothes aren't from a tall shop. Today I'm wearing a striped sweater I got on sale from the Gap with a thrifted scarf and a khaki green jacket from Lands' End with jeans from Tall girl and shoes from Payless. Shirts are definitely the easiest thing to buy in mainstream stores. The long, tunic length is all over the place and I buy a lot of tops at TJ Maxx, Old Navy and Target because I'm poor.
The aforementioned Gap sweater was a bit short when I bought it but I'm in the habit of stretching the sleeves and body of shirts after washing them, then airdrying, to lengthen them out. This might not be great for the clothes but very few of my clothes are so high quality that I care.
If you didn't know already, Payless has women's shoes through size 13. I get sandals there a lot, and you can order online and get them shipped to a store for free.
If you're looking for trendy, cheap jeans, you should probably just do this now. Yeah, it's kind of embarrassing when I get ads for Proactive and the latest YA novel catered toward tween girls with every order, but seriouslyyouguys. $20 jeans with a 37" inseam is not something you give up because they're trying to sell them to 16-year-olds. I know buying jeans from a catalog or online makes some people nervous, but I've bought probably 20 pairs of jeans there since high school and have only returned 2 or 3. If you're a tall teen or young adult (or mature adult with hip style!) check out Alloy if you haven't already.
Two final notes on shoes: Zappos.com is pretty reliable when it comes to large sizes and they have great customer service. And finally--I almost don't want to let this secret out and if any of you readers start raiding the Northtowne Mall is Spokane, WA taking my shoes I will find you--Nordstrom Rack has size 13 and 14, quality shoes at really discounted prices. I can't afford to buy most brands in the regular store but they're really high quality. I stop in there every time I'm driving by and almost always find something. Leather ballet flats for $20? What? You have them in black and metallic bronze? I'll take them both. This spring I bought a pair of suede leather boots, originally $180, for $50 and am reaping the benefits of my thriftiness with this fall weather. It's definitely worth a look.
Of course, every body is different and the things that work for me might not work for you. But hopefully this list will help.
To end this super-long post, I urge you all to add your shopping suggestions to my list. Where do you buy your workout gear, your school clothes, dress clothes, coats? Let's all get together and help the next generation of tall girls avoid the world of man pants and too-short sleeves!