do you use a tool? or just manually make them?
We use something locally based on http://opentcdb.org/ but that does scrum tracking, and draws pretty graphs.
I did use TargetProcess but I now prefer a more tactile method so I draw it manually on a whiteboard.
We tend to just use a simple shared excel sheet with a graph on one tab and a pivot table on another.
We use the community edition of RallyDev and it makes nice burndown charts. The problem is that our team has not yet been able to do a solid job of entering in data to keep the burndown information meaningful.
We also use the community edition of RallyDev that has nice charts. I find it to be an excellent tool once you work out which bits of it you really want to use. There is a huge amount of fields and functionality that most people wouldn't use which could be a confusing problem for bigger teams.
We used to use the tools at rallydev.com, but in time we found the tool to simply be to cumbersome for what we wanted.
In time, I moved to just a simple Excel spreadsheet. Every morning before stand up I counted the hours remaining and added the trend line next to an "ideal" burndown line on the chart. I posted it on the wall where we held our morning standups.
We you Team Foundation Server and with conchango's scrum templates using the built in burndown through this nice little scrum dashboard