Thanks a lot, convinced me of getting NMM

Quick question: if I download a mod from another side than Nexus (so that there is no "download with nexus mod manager" button), for instance TESalliance, how do you install the mod with NMM then?
Sry for the late response - had to head to class -
But you asked something about adding a mod from somewhere other than a nexus site:
If it is in archive format (.7z/.rar/.zip) all you need to do is put it in the "Nexus Mods" folder, (wherever you decided to put that during NMM installation) then re-open NMM, and double-click on your mod.
Just make sure that the mod is zipped with the correct file path. The folders would open something like this if extracted:
Data>Textures>Weapons>Ebony>ebonysword.dds
OR
Data>yourmodhere.esp
Edit:
I think the latest update of NMM fixes that issue, so that if you have 'textures' as the first folder, it will auto-magically put it in the 'Data' folder. NMM is still in beta, so some issues like that are still being worked out. So if a mod doesn't activate right, it's most likely because the mod doesn't have the right file path in the archive.