It's hard to beat good mugs or cups for serving your coffee, but they're not exactly portable. In other words, if you, like us, tend to make your coffee at home in the morning, you will need some sort of vessel to transport the coffee in if you're driving, walking, or bicycling to work.
There are some options: An old fashioned thermos is great, but more optimal for larger quantities. There's the mason jar, but it's not exactly practical, even with a Cuppow (our Cuppow review: Not as good of an idea as it looks; it kinda sucks.) And as far as paper cups go, well, save a tree and all that.
Our favorite solution thus far is the KeepCup. These cups were developed by a pair of Australian baristi who found that most commuter mug were bulky, ugly, and of non standard sizes. The latter was a problem, as the cups didn't fit under espresso machines, and it was hard to get a proper coffee to milk ratio.
Their solution, the KeepCup, is a set of cups that are nicely designed, aesthetically speaking, and that are very usable. The food-grade plastic is lightweight and holds the heat of the coffee without being too hot to the touch. More importantly, the lid sits on the cup tightly, and a plug seals the sipper hole well. When you drink, you can put the plug into a blind hole, and it's neatly tucked away.
In other words, the KeepCup does the simple task of keeping you coffee warm until you're ready to drink it. (Within reason, mind you -- this isn't a thermos.) Like all well designed products it does its job without getting in the way -- that is often easier said than done.
You can get the cups in 4, 8, 12, and 16 ounce varieties, with personalized colors. They are dishwasher and microwave safe, and fit in most standard cup holders. The two smaller sizes should fit with most espresso machines.
As far as an on-the-go travel mug goes, the KeepCup is a well-designed, well-executed product. You should probably give it a consideration for your traveling coffee needs.