New in Debian 5.0 is a new architecture/binary ABI (armel) for current and future ARM processors. Though when it comes to architectures, Debian 5.0 drops support for 32-bit SPARC. With Debian 5.0 "Lenny" there is an enhanced "out of the box" experience as OpenJDK has been integrated for Java support, Gnash / swfdec is available for Flash files, and there is also full support for NTFS file-systems.
The news announcement for the release of Debian 5.0 can be found at Debian.org. The next major release of Debian with an unknown release time-frame has been codenamed Squeeze.