I have a set of x,y coordinates in decimal degrees taken from a Garmin handheld unit.  Does anyone know how to plot those points out in Autocad?  Can this be done from an excel spreadsheet?

Best way for import coordinates is via Autodesk Civil.
For AutoCAD and CSV files (XLS file is possible save as CSV file) you can use utility ascpoint.lsp.
 
uploads/20080810_081645_ascpoint.lspPepaR2008-08-10 08:17:43

Try ImportPoints (freeware and opensource). You can import in AutoCAD mdb  and xls files or txt and csv files. All are converted to autocad points or autocad blocks.abcautocad is an educational institute, but on their web site you can download many useful addons for autocad.. take a look