No locksmith required!
Can anyone be dumb enough to lock their only key in the trunk of their Volvo S60 with a dead battery, AND lock themselves out of the car?!? Turns out, yes.
But I managed to get in, so if anyone else is in this little predicament, here's your solution.
Grab a coat hanger and curl one end into a little 'U' (about the size of a dime). straighten the coathanger.
Pull up the weather stripping on the driverside window from the bottom right corner. once it gets started, it comes up easy.
slide the 'U' end of the coathanger in about 9" and turn it 90 degrees. you'll feel it get caught on the locking mechanism when you pull it up. Otherwise, repeat and turn 90 degrees the other way. it's pretty easy to find.
Pull up firmly and you'll see the lock come up inside the car. open the door.
To get into the trunk you should be able to unlock the car using the power locks and open it, but if your battery is also dead, you can get in through the ski hatch. Right at the very top in the middle, you can see the clasp that locks it shut. Insert a flat head screwdriver, and work the mechanism down until it pops open. Then grab a flashlight and an ice scraper (or whatever you have handy), and use it to pull the seat release handles out to release each seat forward.
Viola! Beats paying $100 for a new key, or calling a locksmith.