All members of Congress are required to publicly file annual financial disclosure reports.  Here's the one for Lieberman for 2005 (dated May 11, 2006).  All I've been able to locate so far for Lamont is this Boston Globe story on his disclosure report.  As a general rule, reports for non-incumbents aren't scanned and maintained by any centralized website, though Lamont's would be available via the Senate public records office.