Today we have some exciting Basecamp API-related announcements.

Blinksale, a web-based invoicing tool from the creative minds at Firewheel Design, now integrates with Basecamp.

Now it’s super-easy to import client names, addresses, phone numbers, and email addresses directly from Basecamp in your Blinksale account for painless invoicing. Simply add your Basecamp account details to your Blinksale Settings page, and we take care of the rest.

Harvest (a web-based time tracking tool) + Basecamp = easy like Sunday morning.

If your organization currently uses Basecamp in conjunction with Harvest for time tracking, things just got a whole lot easier. Harvest admins can now avoid any form of double-entry when it comes to setting up users, clients, or projects. Simply pick the people or projects you’d like to import from Basecamp and you are ready to go. Imported users will receive an automatically-generated Harvest welcome message along with their temporary password.

Phonified has just released a beta mobile version of Basecamp. Phonified Basecamp currently supports Nokia S60 (Series 60) phones, Blackberries, and Palm Treos running PalmOS.

Phonified Basecamp is an application that allows you to access your Basecamp account from your mobile phone. You can download a copy of your To-do list to your phone and update information without having to use a computer. You can also check milestones and configure an alarm on your phone when a milestone is upcoming. Phonified Basecamp lets you read and edit messages and comments, and even upload and download attachments all from your phone. For Premium and Max account holders, you can track time conveniently from your phone as you start and complete tasks, rather than having to remember and update information later.

Headquarters is the first Basecamp widget for the Yahoo Widget Engine. It’s read-only at this time (you can’t modify your Basecamp data). It looks like this:

And our friends at FreshBooks also recently announced that Basecamp integration is coming soon.

It’s really exciting to see rapid uptake and third-party integrations via the Basecamp API. Check out this list of the most popular Basecamp integrations and add-ons. We’ll continue to add to this list as more integrations and add-ons hit the market.

Thanks to all the developers for spending the time on these integrations!