testOaiProvider by Cricket Deane, Digital Library Initiatives, University of Tennesse Libraries, Knoxville, TN.
Based on: http://www.openarchives.org/OAI/2.0/openarchivesprotocol.htm#ProtocolMessages
More OAI help from: OAI for Beginners Tutorial and Encoding Special Characters in OAI Requests.
Open Archives Initiative - Repository Explorer (suggested by Tom Habing): http://re.cs.uct.ac.za/
Select the base URL from the menu. Or type your base URL into the textbox.   About the menu.
Originally written to test 4 different providers and 3 different xtf instances, this menu allows you to switch between different base URLs. The first 2 base URLs work, the last 3 are dummies. You may download the code and create your own menu.
Simple Verbs
Identify, ListSets
Identify, ListMetaDataFormats, or ListSets Request Link will be displayed here.
Verbs With Modifiers
metadataPrefix    from yyyy-mm-dd     until yyyy-mm-dd   setSpec
ListIdentifiers, ListRecords Request Link will be displayed here.
Verbs With resumptionToken
(see Flow Control)

ResumptionToken Request Link will be displayed here.
(harvest one Record)
metadataPrefix identifier
GetRecord Request Link will be displayed here.