1) functions are used for computations where as procedures 
can be used for performing business logic
2) functions MUST return a value, procedures need not be.
3) you can have DML(insert, update, delete) statements in a 
function. But, you cannot call such a function in a SQL 
query..eg: suppose, if u have a function that is updating a 
table.. you can't call that function in any sql query.- 
select myFunction(field) from sometable; will throw error.
4) function parameters are always IN, no OUT is possible

..........................................................................

The Text property exposes the Transact-SQL or other script 
that defines the referenced Microsoft? SQL Server? 2000 
database object.

The FunctionName property specifies the function name to 
call in the Microsoft? ActiveX? script associated with a 
script task or step. 
..........................................................................................................

a. A FUNCTION is always returns a value using the return 
statement. A  PROCEDURE may return one or more values 
through parameters or may not return at all.
b. Functions are normally used for computations where as 
procedures are normally used for executing business logic.
c. A Function returns 1 value only. Procedure can return 
multiple values (max 1024).
d. Stored procedure returns always integer value by default 
zero. Whereas function returns type could be scalar or 
table or table values
e. Stored procedure is precompiled execution plan where as 
functions are not.
f. A function can call directly by SQL statement like 
select func_name from dual while procedure cannot.
g.Stored procedure has the security and reduces the network 
traffic and also we can call stored procedure in any no. of 
applications at a time.
h. A Function can be used in the SQL Queries while a 
procedure cannot be used in SQL queries .that cause a major 
difference b/w function and procedures. 

.............................................................

 1>Procedure can return zero or n values whereas function can
return one value which is mandatory.

2>Procedures can have input,output parameters for it whereas
functions can have only input parameters.

3>Procedure allow select as well as DML statement in it
whereas function allow only select statement in it.

4>Functions can be called from procedure whereas procedures
cannot be called from function.

5>Exception can be handled by try-catch block in a procedure
whereas try-catch block cannot be used in a function.

6>We can go for transaction management in procedure whereas
we can't go in function.

7>Procedures can not be utilized in a select statement
whereas function can be embedded in a select statement.