  This is the first of two papers where we present the analysis of an HST
NICMOS-Cam2 near-infared (NIR) snapshot survey in the F160W (H) filter for a
sample of 78 spiral galaxies selected from the UGC and ESOLV catalogs. For 69
of these objects we provide nuclear color information derived by combining the
H data either with additional NICMOS F110W (J) images or with V WFPC2/HST data.
Here we present the NIR images and the optical-NIR color maps. We focus our
attention on the properties of the photometrically-distinct `nuclei' which are
found embedded in most of the galaxies, and provide measurements of their
half-light radii and magnitudes in the H (and when available, in the J) band.
We find that: (i) In the NIR, the nuclei embedded in the bright early- to
intermediate-type galaxies span a much larger range in brightness than the
nuclei which are typically found embedded in bulgeless late-type disks; (ii)
Nuclei are found in both non-barred and barred hosts, in large-scale ($\gta$ 1
kpc) as well as in nuclear (up to a few 100pc) bars; (iii) There is a
significant increase in half-light radius with increasing luminosity of the
nucleus in the early/intermediate types; (iv) The nuclei of
early/intermediate-type spirals cover a large range of optical-NIR colors, from
$V-H\approx$ -0.5 to 3. Some nuclei are bluer and others redder than the
surrounding galaxy, indicating the presence of activity or reddening by dust in
many of these systems; (v) Some early/intermediate nuclei are elongated and/or
slightly offset from the isophotal center of the host galaxy. On average,
however, these nuclei appear as centered, star-cluster-like structures similar
to those which are found in the late-type disks. [abridged]
