This should be in the Hibernate documentation, but I don’t believe it is.  Instead you have to download the binary distribution and open the readme in the lib directory.  Since I frequently find myself downloading the entire archive just to view the readme, I am reposting the relevant sections here.

ehcache-1.2.3.jar (1.2.3)
- EHCache cache
- runtime, optional (required if no other cache provider is set)

jta.jar (unknown)
- Standard JTA API
- runtime, required for standalone operation (outside application server)

xml-apis.jar (unknown)
- Standard JAXP API
- runtime, some SAX parser is required

commons-logging-1.0.4.jar (1.0.4)
- Commons Logging
- runtime, required

asm-attrs.jar (unknown)
- ASM bytecode library
- runtime, required if using ‘cglib’ bytecode provider

dom4j-1.6.1.jar (1.6.1)
- XML configuration & mapping parser
- runtime, required

antlr-2.7.6.jar (2.7.6)
- ANother Tool for Language Recognition
- runtime, required

cglib-2.1.3.jar (2.1.3)
- CGLIB bytecode generator
- runtime, required if using ‘cglib’ bytecode provider

asm.jar (unknown)
- ASM bytecode library
- runtime, required if using ‘cglib’ bytecode provider

commons-collections-2.1.1.jar (2.1.1)
- Commons Collections
- runtime, required