I have become addicted to the DTrace Toolkit, and use it often to troubleshoot application and performance problems. To ensure timely access to the bits when I need them, I setup the following bourne shell alias to grab the latest version of the toolkit:
alias dtk="cd /opt && /usr/sfw/bin/wget -q -O -http://www.brendangregg.com/DTraceToolkit-latest.tar.gz | gtar xz"
This alias will change directories to /opt, grab the latest version of the toolkit with wget(1m), and uncompress and extract it to the current working directory (CWD).