Back in March, on the eve of SXSW, Plancast got an iPhone app out just in time. Now, with more time to work, they’ve perfected it with the launch of version 2. And that’s not all they’ve been working on.

Over the past couple of weeks, Plancast has rolled out a new site design, a new plan social invitation system, and Eventbrite integration. On top of that, they’re also testing out two other new features: local plans and a recent activity feed. Each of these features make a great service even better.

First off, as I alluded to, the iPhone app is now much improved. Included in this refresh (also made by Leah Culver, who made the first one) is a completely reworked design that cleans up and simplifies the user experience. Also now baked-in is Twitter and Facebook integration to make sharing (and/or signing up) easy. The app is also now iOS 4-ready with Retina display and fast app switching support.

The second new aspect of Plancast is the revamped website. Quietly rolled out at the end of last month, sharing plans from the site is now easier than ever thanks to a more Ajax approach. Co-founder Mark Hendrickson (also a TechCrunch alum) notes that the new share plan prompt was inspired by Quora in that it doubles as both a search box and an input box. The hope is that this will cut down on the amount of duplicate plan entries in the system — arguably Plancast’s biggest weak-spot.

Plancast has also added Eventbrite integration — a very nice addition for the users of that event registration service. Just as with their Facebook Event integration, Plancast will now automatically pull-in any Eventbrite plans you have and populate them on your Plancast profile. Hendrickson notes that we should probably expect Meetup integration next.

A new feature that’s sort of tucked away but may be the slickest one on the site is the cross-site invitations. Now, when you’re setting up a new plan (or inviting people to an existing one) if you simply start typing in the Invite box it will bring up a list of your contacts from not only Plancast, but Twitter and Facebook as well (assuming you’ve hooked up those accounts to your Plancast account). This way, if a friend of yours isn’t using Plancast yet, you can invite them to your event by way of one of those other networks. If you choose their Twitter account, Plancast will tweet at them for you. Or if you choose their Facebook account, Plancast will post on their Wall.

“I haven’t seen anyone do anything like this before, probably because it requires quite a bit of overhead,” Hendrickson says. What he means by this is that Plancast has to continually cache your friend lists from those service and index them so that they can show results as quickly as they do.

Finally, two new features that Plancast is only testing out for now is a new Local tab, and a recent activity feed. The activity feed should be self-explanatory — it will show activity on the site beyond friends simply adding plans. So if a friend comments on a plan or subscribes to a new person, this will show up.

The bigger new feature are the local plans. As I said, this is a new tab on the website that allows you to see the events happening around you. This is a great addition for event discovery as it puts public events out there that people in your social graph may not be attending, but still may be of interest to you. “We’ll be evolving this functionality considerably by letting users filter by popularity and other factors,” Hendrickson says.

You can find the new Plancast iPhone app here. It’s a free download.