Either of these modules should do the trick for you (quotes included are from their project pages):

• Edge Side Includes integration:

  ... is a high performance caching solution for Authenticated users but can be helpful for Anonymous users as well.

   

  Typically, pages which are personalised for authenticated users (even minor personalisations, such as a block which says "Logged in as manarth") will prevent reverse-proxies (which can easily perform 100 times faster than Drupal) from caching the page, because messages intended for one user could then be seen by another.

• Ajax Blocks

  ... permits to load some blocks by additional AJAX request after loading the whole cached page when the page is viewed by anonymous user. It is suitable for sites which are mostly static, and the page caching for anonymous users is a great benefit, but there are some pieces of information that have to be dynamic.

Either of these modules should do the trick for you (quotes included are from their project pages):

• Edge Side Includes integration:

  ... is a high performance caching solution for Authenticated users but can be helpful for Anonymous users as well.

  Typically, pages which are personalised for authenticated users (even minor personalisations, such as a block which says "Logged in as manarth") will prevent reverse-proxies (which can easily perform 100 times faster than Drupal) from caching the page, because messages intended for one user could then be seen by another.

• Ajax Blocks

  ... permits to load some blocks by additional AJAX request after loading the whole cached page when the page is viewed by anonymous user. It is suitable for sites which are mostly static, and the page caching for anonymous users is a great benefit, but there are some pieces of information that have to be dynamic.

http://drupal.org/project/esi or http://drupal.org/project/ajaxblocks should do the trick for you.

Either of these modules should do the trick for you (quotes included are from their project pages):

• Edge Side Includes integration:

  ... is a high performance caching solution for Authenticated users but can be helpful for Anonymous users as well.

  Typically, pages which are personalised for authenticated users (even minor personalisations, such as a block which says "Logged in as manarth") will prevent reverse-proxies (which can easily perform 100 times faster than Drupal) from caching the page, because messages intended for one user could then be seen by another.

• Ajax Blocks

  ... permits to load some blocks by additional AJAX request after loading the whole cached page when the page is viewed by anonymous user. It is suitable for sites which are mostly static, and the page caching for anonymous users is a great benefit, but there are some pieces of information that have to be dynamic.