Ubuntu – simple UNIX command for finding out how many cores I have to work with

Use CPU-Z

Or open task manager and go to the performance Tab. There will be a graph for each cpu in the upper pane.

http://www.cpuid.com/softwares/cpu-z.html

You can use top to list the utilization of each core. Press 1 if necessary to split the CPU row into a separate row for each core.

You can also add a column that shows the last-used core for each process. Press f to bring up the field list, then j to activate the "P" column. Then press space to return to the live view.