There are already plenty of Facebook applications that use Adobe Flash. In fact, according to Facebook, 12 of the 20 most popular apps on the site incorporate it. But until today, developers were left more or less on their own when it comes to building applications that make use of the format.

Alas, the two companies have gotten together officially to make developing Flash applications – both on Facebook and off through Facebook Connect – quicker and easier with the ActionScript 3.0 Client Library for Facebook Platform.

What type of applications does this enable? According to some executives at Facebook and Adobe I spoke with this afternoon, on the high-end, it would essentially let anyone build their own version of the wildly popular CNN-Facebook Inauguration Day mashup.

This was custom built by Facebook and CNN, and made use of AJAX to include status updates side-by-side with live streaming video, after users logged in using Facebook Connect. But with the new Flash libraries, Status Updates could be integrated via Flash, all within the same file as the video. Moreover, anyone could build something like this on their own.

On a slightly less grand scale, it also enables game developers to build far more interactive applications. For example, the UNO for Facebook game we featured last week is almost entirely Flash based. On the Facebook Connect side of the Platform, it could enable things like Web-based photo editors to include a built-in option for uploading to Facebook.

SproutBuilder, the Web-based service for building Flash applications, has already integrated the ActionScript library to allow users to immediately publish their creations as either a Facebook application or a Web app using Facebook Connect. You can check out the details of their implementation in the widget below:

Given the success that Flash-based applications have already seen on Facebook, today’s announcement is an important one for the developer community. As an end-user, all of this probably doesn’t mean too much – other than you’ll likely be seeing more apps on Facebook and off that make use of Flash.

This post is part of Mashable’s Facebook Week. To discuss everything Facebook, join our authors and community at Mashable’s Facebook Page.

If you’re a curious person like me, you like voicing your opinion, finding new movies, reading useful articles, and sharing the best of what you find. There are a lot of social media websites that have these capabilities, but today there is a new entrant to the social media discovery arena: Lunch.

And for Mashable readers, we have invite codes for previewing the site two weeks before it comes out of private beta.

Lunch: An Overview

Lunch’s premise is simple: it is a platform and online community for discovering and sharing opinions and ideas. First, the platform: the company claims that its secret sauce is its Similarity Network engine, which calculates commonalities in tastes and opinions between people. Each rating, review, or game played helps the engine determine your tastes. This helps hook up members with reviews and information on specific charities, products, or ideas that they didn’t even know they were fans of, but that the system calculated.

The second part of Lunch is its community, specifically the reviews: everything under the sun can be reviewed, from a political position to this Mashable article. Reviews can include images and detailed formatting. Users can rate and comment those reviews or have discussions. Lunch’s goal is to replace reading hundreds of reviews and websites on products or ideas, but instead focus on relevant reviews from people with similar interests or mindsets.

The website itself is fun and fully functional. It offers a game called ExhilaRATE where users can compare likes and dislikes against the community, a full array of social networking features, and a bookmarklet, which makes it incredibly easy to review any page or idea. In addition, Lunch’s founder, J.R. Johnson, has had success in the past, most recently selling VirtualTourist to Expedia.

One problem I had was being able to review specific items. I wanted to review cats (cats are awesome, after all), but I could not find a specific review item for “cat” within the first few pages of 299 pages of reviews. The review section needs to be smarter about what users are looking for. It needs an easier way to refine results and reduce clutter.

Lunch – A StumbleUpon for Ideas?

The pitch for Lunch reminded me about another company that focuses on discovering interesting content and providing ratings and reviews – StumbleUpon. StumbleUpon is the popular social media service and toolbar that allows users to find new web content based on previous Stumbles, friend recommendations, and categories.

Although StumbleUpon is based on Web pages and Lunch is based on ideas or “data points,” their purpose is similar. It feel like Lunch may be a StumbleUpon for ideas, but with far more focus on reviews and social networking tools. Founder J.R. Johnson also noted to me that Lunch’s core strength is how well its Similarity Network engine helps target reviews and content based on user interests.

Lunch Invites

Now that you’ve been reading so much about Lunch, you’re probably wondering: where are those invites you promised? To try it out, simply visit the Lunch homepage and click on the section that says “Have an invite code? click here.” Then type in your email and the invite code “Mashable”.

If you give it a try, please don’t forget to tell us what you think of Lunch in the comments.

Twitter has tweaked their sidebar to now refer to Replies as “Mentions,” and adjusted the functionality so that rather than showing only those tweets that begin with your username, they’ll show all tweets that mention it.

While this could already easily be accomplished using Twitter search, or through a client like TweetDeck, it now allows all users of the Web interface – still the most popular method for updating and tracking Twitter – to see everyone who mentions their username.

Twitter’s Biz Stone further explains the move in a blog post: “In your Twitter sidebar you’ll now see your own @username tab. When you click that tab, you’ll see a list of all tweets referencing your account with the @username convention anywhere in the tweet—instead of only at the beginning which is how it used to work. So for me it would be all mentions of @biz. For developers, this update will also be included in the APIs.”

This also means you should also start to see all of the retweets that you generate, since those always start with something along the lines of “RT @adamostrow” or “Retweet @adamostrow.”

A small change on the surface, but one that will give Web users a much better idea of who’s tweeting about them – if they weren’t already getting this information in some alternative way.