After the beta version of iPhone SDK was unveiled last week by Steve Jobs, during a press event at company’s headquarters, today Apple announced that it was downloaded already by 100,000 people.

As you probably know already, the iPhone SDK provides developers with the same rich set of Application Programming Interfaces (APIs) and tools that Apple uses to create its native applications for iPhone and iPod touch.

The iPhone 2.0 beta release includes both the iPhone Software Development Kit (SDK) as well as new enterprise features such as support for Microsoft Exchange ActiveSync to provide secure, over-the-air push email, contacts and calendars as well as remote wipe, and the addition of Cisco IPsec VPN for encrypted access to private corporate networks.

That sounds a lot of interesting features for the developers who want to create new ways to use the iPhone.

On the other hand, Steve Jobs announced the AppStore, which is included in the iPhone 2.0 software. It is a new application that lets users browse, search, purchase and wirelessly download third party applications directly onto their iPhone or iPod touch.

Practically, every developer can submit their applications to the AppStore; Apple would retain 30 percent of all sales revenues.

Users can download free applications at no charge to either the user or developer, or purchase priced applications with just one click. Enterprise customers will be able to create a secure, private page on the AppStore accessible only by their employees. Apple will cover all credit card, web hosting, infrastructure and DRM costs associated with offering applications on the App Store.

Apple is impressed by the interest shown by developers. “Developer reaction to the iPhone SDK has been incredible with more than 100,000 downloads in the first four days,” said Philip Schiller, Apple’s senior vice president of Worldwide Product Marketing.

During last week’s event, developers such as AOL, Electronic Arts, Epocrates, salesforce.com and Sega have already demonstrated applications using the SDK.

Steve Jobs predicted that this summer when the final version of iPhone SDK is set to be launched there will be already hundreds of applications available.

Also, Apple announced iFund, a a $100 million dollar fund aimed at jump-starting third-party iPhone development created by venture capitalist firm Kleiner Perkins Caufield & Byers.

According to AppleInsider.com, who is quoting a partner at the firm, Kleiner Perkins Caufield & Byers “has been so inundated with proposals that it now admits it may have to increase its bounty.”

Last week, Sun Microsystems announced it will release a Java Virtual Machine for the iPhone some time after June, enabling Java applications to run on the popular mobile device.

"We're going to make sure that the JVM offers the Java applications as much access to the native functionality of the iPhone as possible," said Eric Klein, vice president of Java marketing at Sun. Also, Gameloft announced they are preparing 15 new games for iPhone.