The E*TRADE Java SDK by E*TRADE allows developers to access the E*TRADE trading platform from their Java applications. The SDK provides code libraries for handling authentication, accounts, market data, and orders.
Yodlee is extending its platform with an SDK and a new marketplace called the FinApp Store. Recently out of beta, the service enables the creation of apps that exist within the Yodlee interface, to be distributed within its partner services.
Once you get beyond the most basic map mashups, you'll run into a problem with data storage and access, because you can't hard-code hundreds of markers. It's a problem that SimpleGeo wants to fix. And from the looks of their new platform, they've gone beyond expectations.