ESRI's ArcExplorer is a lightweight, no-cost GIS data viewer. Note that the .NET version of ArcExplorer is significantly different from the Java edition.
ESRI offers CSW clients for ArcGIS Desktop and ArcExplorer as part of their free Geoportal add-ons.This client allows you to search various CSW metadata catalogs for dataset and service (WMS, WFS) metadata records within ArcGIS Desktop and ArcExplorer. The discovered services can then be added as a map layer to the GIS application.
The current down-loadable version may not work well with the USGIN metadata profile. Future versions of this add on will likely work out of the box. Meanwhile, we are working on a how-to document to make the client work with a USGIN CSW service.