  (abridged) Deep multi-epoch Sloan Digital Sky Survey data in a 275 square
degrees area along the celestial equator (SDSS stripe 82 = S82) allowed us to
search for extremely faint ($i>21$) objects with proper motions larger than
0.14 arcsec/yr. We classify 38 newly detected objects with low-resolution
optical spectroscopy using FORS1 @ ESO VLT. All 22 previously known L dwarfs in
S82 have been detected in our high proper motion survey. However, 11 of the
known L dwarfs have smaller proper motions (0.01$<$$\mu$$<$0.14 arcsec/yr).
Although S82 was already one of the best investigated sky regions with respect
to L and T dwarfs, we are able to classify 13 new L dwarfs. We have also found
eight new M7.5-M9.5 dwarfs. Four new cool white dwarfs (CWDs) discovered by us
are about 1-2 mag fainter than those previously detected in SDSS data. All new
L-type, late-M and CWD objects show thick disk and halo kinematics. There are
13 objects, mostly with uncertain proper motions, which we initially classified
as mid-M dwarfs. Among them we have found 9 with an alternative subdwarf
classification (sdM7 or earlier types), whereas we have not found any new
spectra resembling the known ultracool ($>$sdM7) subdwarfs. Some M subdwarf
candidates have been classified based on spectral indices with large
uncertainties. We failed to detect new nearby ($d<50$ pc) L dwarfs, probably
because the S82 area was already well-investigated before. With our survey we
have demonstrated a higher efficiency in finding Galactic halo CWDs than
previous searches. The space density of halo CWDs is according to our results
about 1.5-3.0 $\times$ 10$^{-5}$ pc$^{-3}$.
