You can go here for Sketchup v7, but I think (like the v8 trail) it is also a trail version that reverts to "V7 free" after 30 days.

IMO the best free application to handle AutoCad files if you don't have AutoCad is the free DWG TrueView from Autodesk. It can open, view and print every DWG or DXF variety, and it can convert them down to older formats, even to version 10 (late 1980s), if I remember right. Anssi http://usa.autodesk.com/adsk/servlet/pc/index?siteID=123112&id=6703438&DCMP=ILC-DWG-PUV