How to automatically Reset Query Cache for improve table cache hit in MySQL?
The query cache is only helpful for low write, high read workloads and should be pretty handy on a blog with this access pattern. If you issue any DML then you invalidate the QC for that table and repopulation would be necessary. Have you calculated the QC efficiency based on your local status?

http://www.mysqlperformanceblog.com/2006/07/27/mysql-query-cache/

The table cache is a different animal. It caches tables in memory so that MySQL can avoid the overhead of opening them. There's a recipe for tuning this, which is something along the lines of depth of longest join * max_connections but I doubt this us causing you trouble. It's likely that you would be better off tuning the key_buffer (MyISAM's cache for indexes) or the Innodb_buffer_pool_size (InnoDB cache for data + indexes) to reduce load on the server. 

http://www.mysqlperformanceblog.com/2009/11/16/table_cache-negative-scalability/