iGoogle now supports OpenSocial in both the US and Australia, with the plan to roll it out to more users soon. Google also added social features via “Social gadgets for iGoogle” that let you read the news, doing a crossword puzzle, sharing a todo list, or watching a video are all better when done with a friend. Your friends’re able to see what you share or do in your social gadgets either by having the same gadgets on their homepages, or through a new feed called “Updates” that include your recently shared photo albums, favorite comics strips, travel plans and more. “Friends group” help you manage who you’re sharing; you can add and edit friends in this group at any time. If you already have a Friends group within your Google Contacts, you'll be able to easily share with those friends on iGoogle as well. To see some great examples of new (or upgraded) gadgets using social features, check here. Then, when you're ready, take a look at the getting started guide for details on writing your own social gadgets for iGoogle.
More info: iGoogle Developer blog