You're looking for the Metadata API, or already developed tools which use the metadata api.
http://www.salesforce.com/us/developer/docs/api_meta/Content/meta_intro.htm
http://www.salesforce.com/us/developer/docs/api_meta/index.htm
Though using it directly will still require some developement, which may not save you much time. you get metadata in XML, but would still need to process it to what you want to achieve.
Somewhat also depend on the nature of what you want to do. I for instance had a requirement today for 150 custom labels based on an input file. Was much faster to generate metadata XML than to ever do that in the web interface. Deployed the metadata using the force.com IDE.