1. In sql server 2005,There is no option to compress backup files, but in sql server 2008,there you find it.
storing backup file takes 5 minutes without compression in sqlserver 2005,but it takes only 3 minutes in sql server 2008 for storing backup files with compression.
2. Reporting Services no longer requires IIS as it makes direct calls to HTTP.SYS
3. SQL2008 has support for additional datatypes:
date
time
geospatial
timestamp with internal timezone
In additon it has geospatial functions so it can compute differences based on GPS co-ordinates
4. Intillegence window