I'm a little late, but I am going heap praises on my Joemo travel mug. Double sealed, has an inner seal and a pop out top. All metal, no BPA.

http://www.amazon.com/JOEmo-Leak-Proof-Coffee-Travel/dp/B001AYQ8B0/ref=sr_1_cc_1?ie=UTF8&qid=1294335872&sr=1-1-catcorr

I got one for my husband at a local coffee establishment. He's had it about three years. I got one for myself about 18 months ago. Both are holding steady, despite numerous road trips, and one unfortunate fall from a friend's SUV.

Thanks for all the tips! The Thermos Nissan seems like a great option -- I esp. like that it can be both sipped and sealed without much fuss. Farewell, BPA!

Oops. I forgot to provide a link. Here it is:
http://www.amazon.com/Nissan-JMQ400-14-Ounce-Leak-Proof-Insulated/dp/B00004WHWV

I'm the 3rd fan of Thermos mugs. I use the Thermos Nissan - you can sip "on the go" & then tighten the lid & throw it in your backpack & it won't leak. It's stainless steel inside, but with a leakproof plastic top. I think if you want leakproof, you need to have plastic on the top. At least Thermos uses BPA-free plastic.

i love my Innate 17-oz vacuum-sealed travel thermos. HOWEVER it is not for sipping on the go and that is a draw-back. Still, if you don't need to be drinking it while you are driving, it's a great one, keeps your drink hot or cold for hours--just teach yourself how the sealing mechanism works before your first outing with it or you will have drips. The rest of this shopping site is great for all sorts of reusable packages: http://www.reuseit.com/store/innate-bowvalley-double-wall-vacuum-bottle-p-1600.html

We're also fans of Thermos mugs, but don't put them in the dishwasher.

My husband and I have been happy with our Contigo travel mugs. Sometimes you can get 2 at Costco for $20.

Check thermos.com for stainless steel products that are BPA-free (Thermos is committed to it.

http://www.goodhousekeeping.com/product-testing/reviews-tests/food-beverages/best-travel-coffee-mugs

http://www.goodhousekeeping.com/product-testing/reviews-tests/food-beverages/thermal-coffee-mugs

All mine are trade show/vendor giveaways and advertise various products or companies. All will leak eventually, when the gasket on the top gives way. Actually, my favorite is a plastic one with a plastic snap-on lid and no gasket; it's lasted longest without springing a leak, and goes in the dishwasher without complaint. That said, if you don't have access to the giveaways, Coleman makes a good one; get it in the camping/sporting goods section of your local giant discount store.