ok guy,
i had a blackberry myslef.
1 use your bb desktop and click organize
2 it will promt you to save a series of things like contacts, calanders, tasks, memos things like that check each box and go there the steps
3 when doing so it will tell you to choose 4 to 5 things to save it as. pick yahoo
6 next window will tell you to put your password it will send it your mail
now there are 2 ways of doing this. the best way in doing this is when you set up your i phone when setting up your email account it will ask you to want your contacts, calenders, memo's on it. slide it so they say its on.
2nd way... when pluging your iphone click on your phone and your see a new page where it says summery, info, pictures, movies, music... ect. pick info scroll down and click on snyc contacts. it will give your choices use yahoo. when your done click apply on the bottom right corner.
i hope i helped.... maybe somebody can clear it up a little better other then me.
troubledcheech