I would like to know which tools offer support for OWL2, especially for OWL 2 reasoning. Thanks in advance.
Pellet provides OWL 2 support and has a Java API and integration with Jena if you're a Java developer
It's also open source depending on how you want to use it (has a dual licensing model)
TopBraid provides OWL 2 support, particularly OWL 2 RL. See http://www.topquadrant.com/products/TBS_FAQ.html#TBC11
There are several OWL 2 reasoners, including Pellet, Fact++, Hermit, and others. There are several implementations for each OWL 2 profile; Oracle supports something very much like OWL2 RL, as do some other rule vendors. OWL 2 QL is supported in a few systems, including Owlgres, QuOnto, and some others.
OWLAPI is a pretty decent Java API for OWL and OWL2; it handles much of the non-reasoning chores one might have need for (parsing, syntax conversion, some explanation, etc.).
For modeling & ontology building, Protege 4 is a very good choice.
Give the relative newness of OWL2 as a standard, there's a pretty rich and growing ecosystem of tools.
http://tinyurl.com/ydmr2tt gives you an overview of OWL tools but, unfortunately, there is no separate search facet of OWL2 vs OWL. But it may be a good first start. http://www.w3.org/2001/sw/wiki/OWL might give you more pointers
The OWL wiki provides some coverage of tool support. Any RDF tool ought to be able to provide a basic level of support, of course, so check the conformance column to get an idea about reasoning.