SQL Server 2008 new functionality and features
Author Nigel Rivett

At the moment this is just a list.
I'll add and expand when I get time

Data encryption
Encryption key management
Auditing including read audits
Database mirroring and automatic repairs
Hot add CPU
Event handling
Backup compression
Data compression
Resource governor - configurable priorities and resources
Query plan locking
Performance data
Policy based management framework (declarative policy management)
Integration with Microsoft Management Centre
New datetime datetypes
Hierarchy datatype
Table valued parameter
Merge statement
XML enhancements
Filestream datatype
Full text search integration
Sparse data column support
New index types (Spatial, hierachical, filtered)
Loads of stuff for datawarehouses
Partitioned Table Parallelism
Star Join support
Persistent Lookups in SSIS 
Improved thread scheduling in SSIS
LINQ integration
Business entity support
Spatial datatypes
Physical slot function