LOL... like JoyRenee said, your title caught my attention. I can't remember where you live, but I live in Connecticut where the past 2 days have been miserably hot and humid, which I know to be a big contributing factor in the swelling of your feet and ankles. By the end of the day yesterday I couldn't put ANY of my sandles on and I told my husband that it looked like I had hobbit feet (you know from Lord of the Rings... big sausage toes and all puffy looking)... but Shrek is probably a better analogy. =)
Anyway... everything that's been said already works really well (ie: drink more water, put the feet up w/o crossing your ankles, etc)... the one thing that I do that feels really, really good (especially on a hot day) is to plop on the couch and put them in a tub of ice cold water -- throw some ice cubes in there too. Just let them marinade in there until you feel like getting up (I usually do about 30-45 minutes until the water gets room temp).
But I do think driving tends to make them worse too b/c the ugliest Shrek feet I've had so far was when we drove the 6 hours back from upstate NY (baby shower)... they looked and felt hideous.
Your title of this post caught me attention really fast! LOL! Anyway, it sounds counter-productive but you need to drink MORE water. *SIGH* Yes, that's the answer to everything. Drinking more water reduces your water retention. I remember my feet got so fat that I could actually FEEL the water jiggling under the skin (EEEWWWWW).
Also, you should elevate your feet often, as much as you can. With it being hot you're going to sweat and might dehydrate faster than in the winter. So being out in the heat, with tight shoes, will also cause them to swell. Elevate your feet with any opportunity. Don't cross your legs or tuck your legs under you. Sit with your feet firmly planted on an ottoman or stool (don't cross those ankles). Keep the circulation open as much as possible.
get off of them and let them rest. try to elevate them.