I'm doing programming and frequently crash the program (well, it freezes). However, it just remains there in my taskbar (what do we call that in Linux?) and I can't close it. How do I stop it? Is there anything like Task Manager in Windows?

From the command line:

$ ps -ef | grep <program>

Get the associated pid (second field). The grep itself might show up too, ignore that one.

$ kill <pid>

If the process is still there after the above command try

$ kill -9 <pid>

Hope this helps.

also easy:
Run 'xkill' (from console or KMenu-RunCommand), and point the mouse onto the problematic icon on the taskbar. It will "hiddenly" issue a kill -9 onto the hang process.

Cool thanks alot peeps

Use these on the command line:

ps ax
see which processes are running & which PIDs they have

ps ax | grep <name>
The same; select the lines with name in it

ps
See which processes are running from this console

kill <pid>
Try to terminate the process with PID <pid> in a "normal" way

kill -9 <pid>
Force the death of the process <pid> (the process can't escape here)

xkill
Click on the X window which should be closed & killed

killall <name>
Try to terminate all processes with this name in a "normal" way

killall -9 <name>
Force the death of all processes with this name (YEAH)