This is being discussed on a few other threads here currently. I'm a consistent proponent of stored procedures, although some good arguments for Linq to Sql are being presented.
Embedding queries in your code couples you tightly to your data model. Stored procedures are a good form of contractual programming, meaning that a DBA has the freedom to alter the data model and the code in the procedure, so long as the contract represented by the stored procedure's inputs and outputs is maintained.
Tuning production databases can be extremely difficult when the queries are buried in the code and not in one central, easy to manage location.
[Edit] Here is another current discussion
