At my university all of the places you can buy coffee will fill your reusable mug for $1.00, regardless of the size. Otherwise a large coffee is around $1.80... There are lots of places on campus where one can buy reusable mugs too... I am actually cheap enough that I bought a travel mug that specifically fits on my bike and doesn't spill. (OK, confession time: I bought it at Starbucks 'cause it was the only one I could find anywhere that BOTH fit nicely into a bottle cage AND had a good top closing mechanism... so yes, while I bought it to make it possible for me to save money, it's probably just barely paid for itself by now... but it's stainless, so no scary leaching chemicals...).
Maybe a small tax rebate could be offered to businesses that offer incentives for consumers to bring reusable containers -- and maybe a larger one for businesses that require it???? Or something...
I purchased two "boat & tote" type bags that I keep in my car for use at the grocery store too. Every time I go grocery shopping it makes me feel all warm & fuzzy that I'm not taking home 3-6 plastic bags...