Below are the Maximum capacity details related to Indexes Supported By SQL Server:

Max Capacity For	SQL Server 2012	SQL Server 2008 R2	SQL Server 2008	SQL Server 2005
Maximum number of Clustered Indexes on a table	1 Clustered Index	1 Clustered Index	1 Clustered Index	1 Clustered Index
Maximum number of Non Clustered Indexes on a table	999 Non Clustered Indexes	999 Non Clustered Indexes	999 Non Clustered Indexes	249 Non Clustered Indexes
Maximum number of Bytes per Index Key	900 Bytes	900 Bytes	900 Bytes	900 Bytes
Maximum number of Columns per index key	16 Columns	16 Columns	16 Columns	16 Columns
Maximum number of Partitions per partitioned table or index	15,000 Partitions	1,000 Partitions	1,000 Partitions	1,000 Partitions
Maximum number of Statistics on non-indexed columns	30,000 Statistics	30,000 Statistics	30,000 Statistics	2,000 Statistics
Maximum number of XML indexes	249 XML indexes	249 XML indexes	249 XML indexes	249 XML indexes

In Detail:
SQL Server supports:

• 1 clustered index per table.
• 999 Non Clustered Indexes per table for SQL Server 2012, SQL Server 2008 R2, SQL Server 2008
• 249 Non Clustered Indexes per table for SQL Server 2005
• 900 Bytes per Index Key
• 16 Columns per index key
• 15,000 Partitions per partitioned table or index in SQL Server 2012
• 1,000 Partitions per partitioned table or index in SQL Server 2008 R2, SQL Server 2008,SQL Server 2005
• 30,000 Statistics on non-indexed columns
• 249 XML indexes

References:
http://msdn.microsoft.com/en-us/library/ms143432.aspx
http://msdn.microsoft.com/en-us/library/ms143432(v=sql.105).aspx
http://msdn.microsoft.com/en-us/library/ms143432(v=sql.100).aspx
http://msdn.microsoft.com/en-us/library/ms143432(v=sql.90).aspx

Reference : Devi Prasad (sqlserverlearner.com)