A gunman rang the doorbell at the back of an Apple Store in the upscale Clarendon area of Arlington, Virginia. When a female employee opened the door, he shot her in the shoulder and then fled. The employee is recovering, says Arlignton’s ABC 7 news (not to be confused with San Francisco’s ABC 7.) Police are still searching the area for the suspect, and the store isn’t returning my calls. That’s all we know for now.

With so many startups capitalizing on the Twitter platform these days, it’s not surprising that some are crossing into the domain of established sites. One prime example is young marketplace company Tweba (formerly known as Tweebay) which aims to bring the power of Craigslist and Ebay to the swap meet-like community of Twitter, where it allows users to hawk and buy goods as they stream in real time.

The system is relatively simple. Users can choose to login to their Tweba account using their existing Twitter login or their Facebook Connect login. Or they can create a unique username and password. Once signed in, they can list goods they want to sell directly on Tweba, as if they were tweeting normally. Every listing (up to 240 characters for initial posts, and more afterward) includes a link to a picture or more information. Even easier than that, members on Twitter can also add a listing to the Tweba page by including #ihave or #iwanttosell in a regular tweet on their own pages. Hashtags are also used to sort the Tweba tweet stream into goods sold and goods wanted, as well as into categories ranging from #Antiques and #Cars and Aceessories to #Stamps and #Personals (again cutting into Craigslist’s turf).

Here’s an example:

Users who buy goods on Tweba can pay via Google Checkout, Paypal or through an Out of Tweebay Transaction. Just like eBay or Craigslist, the seller than ships the item or items. And just like on eBay, sellers and buyers can provide feedback on one another to ensure good sales in the future. There is an even an auction model that can be tapped into — with users listing items for a set number of days and fielding bids until the listing (which is assigned a particular ID number) expires.

Tweba’s traffic has climbed steadily since March — the site recorded nearly 10,000 unique visitors in May 2009. This might now sound like a lot, but for a new concept that is just six months old, the growth seems promising. It hasn’t disclosed any funding history to date.

Choosing the right sunblock is important, but let's say you're more of a DIY type, or maybe your skin is sensitive to many of the common ingredients. The solution is simple: make your own sunblock.

Instructables user scoochmaroo's detailed guide to making your own sunscreen demonstrates the process either completely from scratch or using a store-bought lotion as a base. She goes as far as to include a chart that gives you measurements for the ingredients based on the SPF you're aiming for.

Follow the link for the "recipe," and make your high school science teacher proud by heeding the warnings about wearing gloves and a mask while blending the ingredients (zinc oxide should be on your nose, not in it).

Have you ever tried a homemade sunblock? What do you use to protect yourself from the sun? Let's hear it in the comments.

A fire in Seattle’s Fisher Plaza appears to have taken down Authorize.net, a service used by online businesses to process credit card and electronic check payments.

That’s a big problem for any Authorize.net customer, since this basically means they can’t accept payments through their websites until the service is up again. I’m told this affects both one-time and recurring payments. With its website down, Authorize has set up a new Twitter account to provide updates and address the many customer complaints and questions. Many of the tweets can be boiled down to, “The team is working hard to get things running again, but I don’t have a timetable”; the company is also trying to reassure customers, “yes we have fully redundant data center” (sic), and also just said, “Transactions are up except for Global processing and Concord. No ETA on those, but we are working on in.”

The service has been down since around midnight Pacific time. I’m also trying to find out how many businesses are affected; TechCrunch says it’s “tens of thousands of e-commerce vendors,” but when Authorize.net was acquired by CyberSource back in 2007, it reportedly had 175,000 customers, and processed 1.1 billion transactions worth $65 billion in 2006.

Meanwhile, TechFlash notes the travel section of Microsoft’s Bing “decision engine” is also down due to the fire. The Bing Travel website says the site should be back up at 5pm Pacific time today.