"Send"
Similar to the "Like" button which can be added to a web page Facebook has introduced, as of April 25th, the "Send" button. It can also be in addition to the "Like" button and coupled with it! This button allows people to share something on the web with specific people in their friend list. It's a very exciting addition to Facebook because it is very versatile. Not only can you share it with specific people, you can share it with anyone via any option the Facebook friend list offers, such as groups! To learn more about the "Send" button just click here to read the Facebook Developer blog post on it.
"Deals"
This is starting out as almost a wave of the future. You can now go to facebook.com/deals and find deals other Facebook users have made available for their businesses. Similar to Groupon and Living Social, Facebook deals are being tested and are available for purchase through Facebook in Atlanta, Austin, Dallas, San Diego, and San Francisco. These deals can be purchased with Facebook credits. The same thing that people have been purchasing add-ons for all of those Facebook games with. The difference between cash and Facebook credits is that Facebook takes a "tax" out of your credits in order to use their services.
On a widespread side, there are also check-in deals available everywhere. These are used through checking-in to the specific business the deal pertains to on Facebook and presenting the deal to the business upon showing up.
"iFrames"
This IS how you build Facebook tabs as of February 14th. FBML has been replaced, but that doesn't mean your FBML tab is irrelevant, it just means it's outdated. Don't you love the speed of technology progression?! Essentially it comes down to the iFrames tab being much more versatile in general. The customization of iFrames tabs is simplistic and specific. You can now make your tab branded with your website/business! It also can integrate google analytics which allows you to monitor the click-through rate of whatever you've posted within your tab. And last but certainly not least, you may have noticed that any links you provide within the tab will actually open up within the tab. Some people see this as annoying, but some people see this as revolutionary! Stats show that this actually produces more conversion rates to leads because people who are using Facebook don't want to leave Facebook. The thought is that this feature simply enhances the Facebook experience!