I just submitted Block Cache Alter for Drupal 6 which lets you alter cache settings per block on the configuration screen. Cache settings per block are now set in code, but if you don't like the default - usually none, you can now easily change this. Install this to speed up block rendering for authenticated users.
There are also two patches in the D7 queue now that might interest you:
- Currently block caching support in views 2 is disabled, probably until 235673 gets in and backported.
- I submitted this module as a patch (imagine how small it is) as a feature request for D7, review it on #347350.
Off-topic, I'm still looking for another maintainer for PicLens. File an issue and I'd be happy to move it over.