Tor primer, for those living under the privacy rock:

Tor is a software project that helps you defend against traffic analysis, a form of network surveillance that threatens personal freedom and privacy, confidential business activities and relationships, and state security.

And a bit on TorFlow:

TorFlow is set of python scripts written to scan the Tor network for misbehaving, misconfigured, and overloaded Tor nodes.

Get TorFlow via subversion:
svn co https://svn.torproject.org/svn/torflow/branches/gsoc2008/ torflow

soat.py will check routers for certain restrictions and misconfiguration.
This command will create a csv of routers with restrictive policies. You can add these to your torrc after excludenodes.
./soat.py --policies | grep but | awk '{print $10}'| sort -u | awk '{printf $1","}' >> banlist.csv
I recommend that you double check them because it may cause tor to stop working

You can use speedracer to create a list of slow routers as well:
./speedracer.pl > buildtimes.txt
cat buildtimes.txt | grep build | awk '{print $13" "$11}' | awk '{if ($2 > 60) print $1}' | sort -u | awk '{printf $1","}' >> slowlist.csv
Make sure you edit speedracer.pl and tsocks.conf if you experience problems.

While I’m on the subject of excludenodes, did you know you can exclude by country code in newer versions of tor (>=0.2.1.6-alpha)?
ExcludeNodes AR,BR,CA,DE,IL,JP,MX,US

Ubuntu 8.10 users can obtain 0.2.1.7+ by doing the following:

Add to /etc/apt/sources.list
deb     http://mirror.noreply.org/pub/tor experimental-0.2.1.x-intrepid main
deb-src http://mirror.noreply.org/pub/tor experimental-0.2.1.x-intrepid main

Add the keys
gpg --keyserver subkeys.pgp.net --recv 94C09C7F && gpg --fingerprint 94C09C7F && gpg --export 94C09C7F | sudo apt-key add -

Install new tor
sudo aptitude update
sudo aptitude install tor
or just upgrade your old version
sudo aptitude update
sudo aptitude safe-upgrade

Remember to make backups of your torrc so you can easily recover from screwups caused by not following directions