Fan pages are a great way to make some money. However you need to send them and have targeted visitors that are related to your niche. Being a developer would also make you some nice cash. Good luck!
I am also interested in Facebook monetization. For those who do it. How effective is it to advertise on Facebook?
You want to advertise or want to earn through advertisements? In both ways its quite effective. If you want to promote your website or service then you can target users through facebook advertisements. If you want to make money then you can show advertisements which will generate you revenue. The key point is building good content (application, fan page etc.) and then getting users. Money will automatically come.
Monetizing through FB ads is very effective. But make sure you think-out your niche in-depth and target the users perfectly or you could risk losing alot of money.
Any facebook app creators here. I am looking for a guide to use FBML as well customizing fan page, using XFBML.
You can always visit sites that sell ready-made Facebook application scripts. My business partner's site is http://mporgsoft.com/.
Facebook PPC Ads, of course! You could also make a fan page, but you'd have to offer something GOOD in return to get and keep fans..