To add to Steve's comments, on the RRSP and home/car front:
Yes, on RRSP (depending if you really need it
then your choice about cashing in but being taxed), leave it, but look into having access to it (ie inquiring about it, making periodic switches etc) while in the US thru your dealer (ie if bank or brokerage firm, contact them and ask if they're definitely registered to deal with you in the state you will be in). Otherwise, switch your dealer (or bank), before you move down.
Banking: advise that you retain your current Cdn bank acct (ie say chequing) with minimal (<$500). That way, keep your client card, and allows you access, for whatever reason, if back in Canada temporarily. If need be, allows some payoff of your Cdn credit card during initial transition etc.
Home/car: Well, simply open a bank acct in US, or (like RBC which has RBC Bank USA-Centura) transfer most funds to US account upon moving.
There is nothing preventing you to buy a car, I did, and on loan,but had first setup my US bank account/job verification. Straightforward. Renting a car.well usually require a credit card. They will accept major Cdn credit cards, and your Cdn drivers license. But I would also quickly obtain your US drivers license (not a big deal, just go in and do it), because that ID is very powerful (ie for rentals,etc) in addition to your passport.
As for housing, I would HIGHLY recommend rent for 1-6mths first. I am presently here in the US, and the housing market is in a major downturn everywhere. Credit is hard to get for most people, and with prices decreasing, not a smart time to buy JUST YET (am projecting perhaps Spring 2009.). Depending who you rent from, they may ask for credit history, but most (if thru a Realty) can do a Cdn credit history check (they may charge you for it, prior to approving your lease etc). Another way around it is to get perhaps a credit letter from your current Cdn bank, before you come down, with contact#s.this works exceptionally well and shows you're proactiveness (always a plus).
Now, with for instance, RBC USA (or others ie TDW etc) they will recognize your Cdn credit history, and thus be easier to obtain a mortgage later thru them, and/or can leverage their contact info if you get setup with another US bank.
As for
taxes, thus move anything/everything
(ie cash etc) to the US. Thus doing your US
taxes will be easier when everything is here.thus leaving perhaps only your RRSP.
Cheers, good luck!