I believe that the BDSalem client allows you to mark one spot, but it is not persistent across sessions (so if you log out, its gone). I use Enders, though, so I could be incorrect.
However, finding your way back to your claim is fairly simple using a custom client and the Salem Map Tool, all of which you can find linked here:
http://salemwiki.info/index.php/3rd_PartyMy method is to find some sort of landmark on the minimap that I will remember (like a quarry or strangely shaped marking), and find my way from there.