I apologize if this has been discussed before but I just found an iphone app called Diabetes Pilot...it's $11.99 but it is well worth it! Here is a link
It even tells you how much insulin to take to reach your target range...and pretty shnazzy graphs.... at least for me it's really cool may not be your cup of tea :D
There is a desktop app, too, that costs $40 but has even more features. I haven't bought it(though I have the iPhone app) but have used the 30-day trial. It syncs up with the iPhone perfectly.
I used this program extensively. I liked that it has a desktop component to print reports. There are some good apps out there. I did find the database a bit limited. There are some database programs that can help with carb calculation. A good one is CarbsControl -- it also has nutritional information for many chain restaurants. Calorie King I think also has a very rich database as well.