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Our venture capital roundup for the day features a range of companies raising large and (relatively) small amounts of money. We've got software for school teachers to keep their classrooms organized and an app to make keyword advertising easier for small businesses, among several other useful technologies. We want to know which of these companies you'd like to keep tabs on. And as usual, we're announcing yesterday's poll winner.

Hubspot has just announced a Series D round of funding for their marketing-as-a-service platform. Investors include some very big names like Google, Salesforce and Sequoia, which shows how much interest there is in its service aimed at small businesses. It's also a big boost for the Boston startup scene, as Hubspot is now one of the fastest growing SaaS companies in history by revenue, only behind Salesforce according to their CEO Dharmesh Shah.

Along with main competitors Eloqua and Marketo, Hubspot helps small businesses move away from traditional cold-calling and display advertising and into the new world of social media, search engines and blogging. On my recent visit to Boston, Shah explained to me that the initial idea came about when he noticed how much traffic he was able to drive through his OnStartups blog, when many of the businesses he was helping were struggling to get a fraction of the exposure.

As we wrote last week, the most common mistakes that SaaS providers make often involve errors made while balancing the incoming subscription receipts with the need to go out and spend some money to acquire new subscribers.

Dharmesh Shah, CTO and founder of HubSpot, recently blogged his thoughts on a similar topic: the insights he's gleaned from the B2B SaaS startup. Describing these as "non-obvious SaaS startup lessons," Shah's blog post contains a list seven important observations.

It's not every day you get the chance to hear a half dozen executives from successful startups speak openly about how their companies managed to get to where they are. In fact, its most likely that to get that kind of access in one day, you'd have to be at some high-priced convention that costs several hundred dollars to attend. This isn't the case, however, with Starter Day, an event hosted by software makers Atlassian that will showcase six CEOs and founders from various startups, including Boxee, Aardvark and Pandora.

After news about the landing of US Airways 1549 in the Hudson first broke on Twitter in January 2009, the microblogging service quickly captured the imagination of a new group of potential users. Throughout the first months of 2009, Twitter grew at a rapid pace, peaking at a growth rate of 13% in March 2009.

Now, however, according to the latest data from HubSpot, Twitter's growth is slowing dramatically. In October 2009, Twitter's growth rate had fallen to 3.5%. On a positive note, though, the average active user on Twitter today is more engaged than six months ago.