SharePoint Branding Tool (Themes, Master pages, Site Logos...)

This tool can be used apply the following actions for multiple Site Collections, and Child Sites:

modify Themes
modify MasterUrl (Master Page)
modify CustomMasterUrl (System Master Page)
modify SiteLogoUrl (Site Logo)
modify SiteLogoDescription (Site Logo Alternative Text)
modify AlternateCssUrl (Custom CSS Style Sheet)
view various properties of sites and themes at a glance
Selection of sites can be filtered by the Site Template used.

http://www.codeplex.com/BrandingTool