We’re big fans of HootSuite at AllTwitter – Lauren and I both use the software extensively for all things Twitter, both professionally and with our personal accounts – and I’m very pleased to see the company announce a major milestone this morning: HootSuite has now reached two million account sign-ups.

More impressively, they’re doubled their userbase from one million to two million in just seven months.

Writes HootSuite:

We can’t help but feeling like we hit the 1 million milestone just months ago… likely because HootSuite grew to 2 million sign-ups just 7 months after achieving the seven digit threshold in Nov. 2010 ~ whew. We managed to keep up this pace by listening carefully to how the wide range of customers are using HootSuite – whether for business or pleasure – and adding the tools to help you meet your objectives.

Thanks to all of you who shared your thoughts, ideas and opinions and especially to all of you who told your friends and colleagues about your “secret weapon” – you make our jobs remarkable.

They’ve even put together a very cool infographic:

For more insights into the HootSuite culture and this new milestone, visit their official blog.