Linden Lab Offically announced the roll out of mesh to the main grid this morning, 11:32 AM PT/SLT. See the announcement here: Mesh Update.
There are requirements for being able to upload mesh and the ability is limited for now. The first requirement is to take an Intellectual Property Rights tutorial in the form of a questionnaire. You can find it here: Your SL Dashboard.
You must have Payment Information on File (PIOF). This is so that they have positive proof who you are for IP Rights enforcement.
You must use the Mesh Project Viewer. They link you to a specific version of the viewer in the next requirement.
You must be a member of the Mesh Live Volunteers Group. See the Wiki page that is here: Mesh/LiveVolunteers. Join this free group and make it the active group. In the first part of the text is a link to the test viewer. Download and install it. If you have been using a Mesh Project Viewer this version will overwrite it. I’m not sure how easy it will be to run more than one Mesh Project Viewer. The viewers do use separate settings files. One is named settings_aditi_projectviewer-mesh.xml and settings_projectviewer-mesh.xml.
Makes sure you install it in a separate folder from your other Mesh Project Viewer, if you want to use both version of the Mesh viewers.
If you just want to see mesh, all you need to do is get either the Mesh Project Viewer or Kirsten’s Viewer. The Mesh Project viewer installs in its own folder, so you can run the standard SL viewer and the Project viewer. Logon with either viewer.
Join the Mesh Volunteers Group and make it your active group. Search on mesh volunteer and the group will come up.
Open the World Map and search for a region named Mesh. You will get a list of the mesh sandboxes. TP to any one of those and start cruising around. There is some amazing stuff there.