MOSS Hard Limitations

SharePoint 2007 Maximum Limitations
Following is a list of names and other parameters with the maximum allowable size on each. If during your course of using the product, you inadvertently cross these limits, then you would end up with errors. These are hard limits

Site Name	128 characters
Site URL	255 characters
Display name	128 characters
Connection string	384 characters
Email address	128 characters
Version numbers	064 characters
Virtual Server Friendly Name	064 characters
SQL Database Name	123 characters
SQL Database Column	128 characters
SQL Database Table Name	128 characters
SQL Role Name	128 characters
Server Name	128 characters
Windows User Name	300 characters
Windows Password	300 characters
Dependencies per object	032 objects
Zone enumeration value	004 zones
Default SQL command timeout	300 seconds
Number of simultaneous workflows that can be run	* 015

For some more Limitations refer http://technet.microsoft.com/en-us/library/cc262787.aspx