Looking for a mug that won't spill when bumped? This might be a good solution. The Mighty Mug is a leak-proof mug that won't fall when bumped from the side. It has a special mechanism that keeps the mug in place unless lifted straight up.
Product reviewed by Jen:
Jen did an initial test of this mug and found that it is indeed very resistant to being knocked over when placed on a hard, flat surface. However, she had a more difficult time releasing it, because the cup needs to picked straight up -- not at an angle (i.e., towards you). Also, the flip top to open the mug might be a great design for some individuals but was difficult for Jen. This could be a great cup for some individuals with decreased fine motor control or coordination, but it was not the best fit for Jen.
That said, the Mighty Mug product video offers a good demonstration of how this product works and might help you determine if it's a good product for you. They offer a 100% happiness guarantee, and it comes in many colors and varieties (including a tumbler with a straw!).