Sharepoint 2010 supports following authentication methods-
1. Claims Aunthentication:- Claims authentication is buils on windows identity foundation which is a set of .Net framework classes that are used to implement Claims based identity.
2. Windows Authentication:- Standard IIS windows authentication methods are supported.Below are the following types of windows authentication:
a. Anonymous
b. Basic
c. Digest
d. Certificates
e. Kerberos
f. NTLM
3. Form Based authentication:- Forms-based authentication enables SharePoint Server 2010 to work with identity management systems that implement the MembershipProvider interface. Below are the following types of FBA authentication:
?Lightweight Directory Access Protocol (LDAP)
?SQL database or other database
?Other forms-based authentication solutions