Great summary by Phillip Pearson on the Feedmesh list

The feedmesh and related ping-distribution services, so far, in
alphabetical order:

  • blo.gs distributes pings in a streaming changes.xml; see
    http://blo.gs/cloud.php for info, or telnet to ping.blo.gs port 9999
    for the stream.

    Info distributed: blog name, blog url, feed url, ping time

    NB: the stream is currently uncompressed, but will become
    zlib-compressed at some point in the future.

  • pingomatic.com collects pings and distributes them by pinging a
    number of other services. Contact the operators to get them to ping
    you too.

    Info distributed: blog name, blog url (maybe rss url?)

  • pubsub.com distributes pings and post info in a XMPP stream; see
    http://www.pubsub.com/docs/pubsub_xmpp_draft.html for info, or
    telnet to xmpp.pubsub.com port 5222 for the stream (but read the
    tutorial at http://groups.yahoo.com/group/feedmesh/message/112
    first, as some work is involved to get data out).

    Info distributed: lots of blog info, lots of post info

  • topicexchange.com distributes pings in a traditional streaming
    format; see http://www.myelin.co.nz/post/2003/12/16/#200312161 for
    info, or telnet to topicexchange.com port 9123 for the stream.

    Info distributed: blog url

  • weblogs.com distributes pings in an XML file that you can poll. For
    24 hours of ping data, read http://www.weblogs.com/changes.xml. For
    5 minutes of ping data, read
    http://www.weblogs.com/shortChanges.xml.

    Info distributed: blog name, blog url, ping time