Yes, there are several. Most will be a quite a bit lighter than Aloft (though most concentrate on re-skinning Blizzard's default nameplates in various ways, and may not be as featureful).

These addons are as follows. Acapela has not tried most of these (your mileage may vary).

Themed nameplates: TidyPlates. Numerous themes are available.

Reskinned namplates with class icons: caelNameplates.

More Reskinned nameplates (based on caelNameplates): dNamePlates.

For the atrUF unit frame system: atrNameplates.

Arena nameplates (with castbars on all nameplates): Overhead

Nameplate modifier (user-generated skins): NameplatesModifier

Lightweight nameplates: AtheneNameplates

New:

Lightweight nameplates: pNameplates.

Docs UI Nameplates; this is a beta, the URL may change without warning.

Namplate Buffs: PlateBuffs (this may interoperate with Aloft, I have not tried it yet).

System for nameplate distance/perspective: _VirtualPlates; works with Aloft and others, adjusts nameplate sizes seamlessly as a function of their distance to the camera, to reduce screen clutter and provide visual cues to unit proximity. This works in 3.2 (though it seems to hide nameplates intermittently). It seems to have problems under WoW 3.3 (hopefully the author can figure out some workarounds).

NOTE: VirtualPlates has been deprecated, broken by a patch somewhere along the way.

Please send a PM to Acapela if there is an addon you would like included here.

There is also a nice list at Vranx (the whole site is generically useful).