Free up space in magento and manually delete magento cache.

SQL queries to clean most of the log and extra data that is not mandatory.
Don't use it if you need to debug problems or if you are exporting/importing data.

TRUNCATE dataflow_batch_export;
TRUNCATE dataflow_batch_import;
TRUNCATE log_customer;
TRUNCATE log_quote;
TRUNCATE log_summary;
TRUNCATE log_summary_type;
TRUNCATE log_url;
TRUNCATE log_url_info;
TRUNCATE log_visitor;
TRUNCATE log_visitor_info;
TRUNCATE log_visitor_online;
TRUNCATE report_viewed_product_index;
TRUNCATE report_compared_product_index;
TRUNCATE report_event;
TRUNCATE index_event;
TRUNCATE catalog_compare_item;

Note: Not all the tables are available on versions before version 1.8

You can freely delete in the web root folder

logs - var/log/*

cache - var/cache/*
reports - var/report/*










exports (your exported data!!!) - var/export/*
 session (also your current sessions - if they are saved in those files) - var/ssession/*
 temp files (usualy the folder is empty) - var/tmp/*



Before doing anything just backup your data and make sure that you don't need logs and other stuff.