I love command-line stuff that helps me develop software quicker. Here are a couple commands that will make your development life a little easier. Got any more? Leave a comment with a command line utility that really helps you with your job.
Find all ports listening over TCP (great for seeing if a service is listening over TCP correctly):
netstat -a -n -o -p TCP | findstr LISTENING
tasklist /m "mscor*"
Find an assembly by name or other attribute in the Global Assembly Cache
gacutil /l | FINDSTR your_find_value_here
Create a script for configuring SQL Server for all ASP.NET 2.0 features.
aspnet_regsql -A all -sqlexportonly your_sql_script_file_here