SOFTIMAGE|XSI is the most advanced 3D animation software for games, film and television. Now you can model, animate and render with unparalleled performance. The XSI Gigapolygon core, capable of handling massively detailed models with millions of polygons, is the number one reason why leading entertainment companies are switching their next generation projects to XSI. Built on the newest code base and designed for the way the artist thinks, XSI empowers you to bring your creative vision to life.
Tutorials: Softimage Video Tutorial Series
Current Version: www.softimage.com/downloads/XSI_Trial/default.aspx
a FREE version of Softimage for Game moding ( exports to Unity with FBX etc ) can be downloaded here 
Autodesk® Softimage® Mod Tool software (formerly XSI Mod Tool) is a free 3D modeling and animation package for creating noncommercial games and "modding" (modifying games). Autodesk® Softimage® Mod Tool 7.5 is based on the same professional toolset found in Autodesk® Softimage® 7.5 software, used by game developers to create 3D characters, levels, props, and animation.
Free for Noncommercial Game Creation and Modding
Free to download*—Download now. For aspiring game artists—Aspiring game artists can get started with professional tools to help create 3D characters, props, levels, and animation for games.
Export to Other Engines, FBX, COLLADA Add-ons are available that enable export to Crytek CryENGINE® 2, Valve® Source™ engines, and Epic Unreal Engine 3. Softimage Mod Tool 7.5 also exports Autodesk® FBX® software and COLLADA files for engines that support it.
Unity Scale Calibration
when creating custom rigs you can use nulls or object as bones in FK chains when exporting to unity using crosswalk.
Exporting to Unity
no issues with export as OBJ from softimage
animated objects guide- make sure you have the latest version of crosswalk from autodesk 
best to make your own rig you can only envelope to FK chains, export using FBX and Unity will read the animation without issue.
Use simple materials only. If you have generated normal maps for your object in XSI it's best to assign a new material before exporting. Only connect a texture to the diffuse port of your new illumination shader and export using FBX. Connect the normal map in Unity.
On the crosswalk export options panel turn off Camera and Lights