'Check for update' component freely available?

Question

Do you know of a freely available (preferable FOSS) implementation of the ubiquitous 'Check (online) for a new version' functionality?

.NET is preferred.

What would be even more interesting, would be a mechanism to allow the download and install of the update(s) in case they are available.

Answer 1

Here's what i did - before I switched to clickonce:

    private static readonly string LATEST_VERSION_FILE_URL =
        "http://foo.com/Version.txt";

    private static Version GetCurrentVersion()
    {
        Version v = null;

        try
        {
            using (WebClient wc = GetWebConfiguredWebClient())
            {
                string latestString =
                    wc.DownloadString(LATEST_VERSION_FILE_URL);

                v = new Version(latestString);
            }
        }
        catch (Exception e)
        {
            Program.LogDbg(e.ToString());
        }

        return v;
    }

Answer 2

ClickOnce from Microsoft is a good and a free option.