The Weight Watchers website has a BMI chart and an ideal weight range chart, you can find them here. Bear in mind that BMI isn't the best way to measure a "healthy" size - although given that it's athletes who really come out badly on the BMI charts, we probably don't need to worry too much about that
Lighterlife do a rather alarming BMI chart here, but that one just serves to make me very depressed as the figure balloons out to show how I must look!
I'd say not to get overly bogged down with ideal weights and figures just yet. I don't know about anyone else but I find that looking at ideal weights, and then thinking about the amount of weight I need to lose to get there, is soul destroying. I find it better for my head to not look so far into the future, and concentrate on the here and now - it's better for me if I look at a series of achievable short term goals for now, and just concentrate on each one as I hit them.
Although as I've spent the last two years losing and gaining the same old two stone, I may not be the best person to listen to ...