Sun Microsystems always seems to be forced to defend itself, whether it is the company’s ongoing strategy amid dimmed revenue and earnings or its participation in open source. As one who recently considered the fate of a somewhat weakened Sun, I’d also like to highlight a recent series of promising technologies and efforts — dominated by open source — from the venerable technology giant.

Despite continued doubts, Sun continues to focus its strategy on open source software, which is finding its way into the company’s Solaris OS, storage technology with ZFS file system and MySQL database and elsewhere. The company recently launched a new Web site where it is figuratively letting its open source ponytail down and more succinctly staking out its place and participation in open source.

One of the most obvious places Sun is putting open source to work is its Solaris OS, released in its latest form this week. Key among the highlights for the updated Solaris is the use of the open source ZFS file system. Similar to how Red Hat draws on the Fedora community and distribution for its Red Hat Enterprise Linux, Sun is taking ZFS from OpenSolaris, which continues to grow (yes, it’s true Linux has many vendors behind it and OpenSolaris only has Sun). Although Sun may still be struggling with some internal conflict over support for Linux alongside Solaris, the company deserves credit for successfully growing Solaris technology from the open source, OpenSolaris community.

ZFS is also playing a role alongside other Sun products, including Thumper servers, in Sun’s Open Storage initiative, which has grown business and revenue since launched more than two years ago. Although many believe Sun would be better off without its legacy hardware and systems business, here we see the company putting open source to work again for a promising, emergent story on storage.

Sun, which oversees the Microsoft alternative office project OpenOffice.org (rooted in Sun’s StarOffice software), is also broadening its backing of the OpenDocument Format, launching the ODF Toolkit Union with fellow ODF supporter IBM. We have seen some concerns about Sun’s oversight of OpenOffice.org and impact on ODF. Although there will still be challenges for Sun to effectively promote OO.o development and proliferation and the ODF, the ODF Toolkit Union seems a wise move to avoid the same issues with ODF, which last May won support from Microsoft in its own Office 2007 and subsequent Office software.

Another area where we don’t necessarily hear much about Sun, but where 451 Research Director Rachel Chalmers highlights the company is active, is virtualization. Sun’s open source xVM Server and related xVM Ops Center 2.0 help the vendor maintain an enviable fourth spot in the growing virtualization market, behind VMware, Citrix and Microsoft.

Sun has certainly been stung by its lowered outlook and earnings and an economic slump that has further erased high-end server business, but the company’s technology and its focus on open source continue to drive its relevance in the industry. Its biggest challenge now is, fittingly for its open source identity, converting that relevance to revenue.