You can use h5dump (HDF5), hdp (HDF4) or HDFView (for both HDF4 and HDF5) to dump data into an ASCII file that can be imported into Excel.

h5dump: (HDF5)
You can convert HDF5 files into ASCII (comma delimited) that can be imported into Excel, without it wrapping the lines. You would use h5dump with the -y and -w options:

   h5dump -o dset.asci -y -w 400 dset.h5

Note that the value that is specified for the -w option must be the dimension size multiplied by the number of positions and spaces needed to print each value. (So be sure to specify a value that is big enough!)

hdp: (HDF4)
You can convert an HDF4 file into an ASCII file (space delimited) that can be imported into Excel, without it wrapping the lines. Use hdp with the -d and -s options. For example:

       hdp dumpsds -s -d -n "data1" sd.hdf > & sd.asc

HDFView: (both)
You can also open an HDF4 or HDF5 dataset with the TableView (spreadsheet) in HDFView, and then select "Export Data to File", to obtain a tab-delimited ASCII file that can be imported into Excel.