You'll be seeing a lot of potty training related posts in the next litthe while since we are deep in the midst of Buttercup's PT University.
I've had a potty chair in the bathroom for almost a year now just so she could sit when she wanted and get used to it being there. I waited until she turned 2 to get busy after taking a minute to make sure she was showing signs of readiness.
One nifty little contraption is the Potty Watch from One Step Ahead. It's cheap (10 bucks!), cute (I got the pink one!), and makes it fun for kids with musical reminders for when it's time to try and potty. We set ours for every 30 minutes right now, and it's working a lot better than the battle of wills that ensues every time I asked if she wanted to try going potty. Just make sure to save the directions. I've had to refer to them a few times to refresh my memory on how to access the different modes available.