Every now and then i see a question pop up that asks what is the max this or that in sql server?

Well here are some maximum values:

Bytes per short string column
8,000
Bytes per GROUP BY, ORDER BY
8,060
Columns in GROUP BY, ORDER BY
Limited only by number of bytes
Bytes per index key
900
Bytes per foreign key
900
Bytes per primary key
900
Bytes per row
8,060
Bytes per varchar(max), varbinary(max), xml, text, or image column
2^31-1
Characters per ntext or nvarchar(max) column
2^30-1
Clustered indexes per table
1
Columns per index key
16
Columns per foreign key
16
Columns per primary key
16
Columns per base table
1,024
Columns per SELECT statement
4,096
Columns per INSERT statement
1,024
Connections per client
32,767
Database size
1,048,516 terabytes 
Databases per instance of SQL Server
32,767
Filegroups per database
32,767
Files per database
32,767
File size (data)
16 terabytes
File size (log)
2 terabytes
Foreign key table references per table
253
Identifier length (in characters)
128
Instances per computer
50 (Workgroup Edition only 16)
Locks per connection
Maximum locks per server
Locks per instance of SQL Server
Up to 2,147,483,647
Nested stored procedure levels
32
Nested subqueries
32
Nested trigger levels
32
Nonclustered indexes per table
249
Parameters per stored procedure
2,100
Parameters per user-defined function
2,100
REFERENCES per table
253
Rows per table
Limited by available storage
Tables per database
Limited by number of objects in a database
Partitions per partitioned table or index
1,000
Statistics on non-indexed columns
2,000
Tables per SELECT statement
256
Triggers per table
Limited by number of objects in a database
UNIQUE indexes or constraints per table
249 nonclustered and 1 clustered
User connections
32,767
XML indexes
249

For a complete listing go here.