I've had RLS during my last two pregnancies and this one. It seems to get worse and worse with each one, gar. While nothing can totally relieve it, some things that help A LOT are:
yoga before bed (there are some great prenatal ones you can check out on youtube, your library, fitness tv.com or even ondemand if you have cable).
Magnesium- increase your magnesium intake. You can do this with foods or supplements.
X the Tums- calcium in excess (like if you're popping tums like there's no tomorrow) can interfere with absorption of MANY important nutrients, and can contribute to pregnancy related RLS and anemia, among other things.
a night time routine- just like with insomnia (which you may or may not have) having a routine and heading to bed at around the same time can really help. Also, eating a complex carb and sleep assisting food, turning off the tv or iphone or computer (any screen) at least a half an hour before heading to bed, stop drinking water an hour or so before bed, read or listen to soft music NOT in your bed (reserve for sleeping, not hanging out), dimming your lights or not using as many a half hour before bed (increase serotonin), all of this can all help prepare your body for sleep.