Linear Technology has released a version of LTSpice for OS X. I just downloaded it and started playing with it so I don't know yet what works and what doesn't. It's a very minimal interface at this point, but I have run a couple of simulations on it and it is working. Not bad timing either since Wine is now broken on my machine and I couldn't run LTspice under Wine anymore.
http://www.linear.com/designtools/software/ (http://www.linear.com/designtools/software/)