This can be done in ArcMap 10. In the TOC, right click on the layer of interest and select Data -> View Item Description. With "core" (i.e. before SP 1 for ArcGIS 10), there's a bug NIM059008 that caused the launch of the Item Description to fail. The workaround can be accessed at: http://forums.arcgis.com/threads/9171-bug-viewing-metadata-in-ag-10 Once you install the workaround, you can access metadata in ArcMap without the need of Catalog if you wish.
