I have long wanted to be able to create in-cell sparklines in OpenOffice calc. There are a few commercial tools to do this, but they are made for Excel, and also they are proprietary. I've put together enough of a solution to prove the concept. The idea is to create a font containing bars, lines, etc., and then an OpenOffice macro generates strings of characters in this font from the spreadsheet data.
Then I wrote some simple OpenOffice macros to generate characters in this font from the spreadsheet data.
To use it, install the font on your system, and import the macros into OpenOffice. Then, in a cell where you want a sparkline, do
=SPARKLINES(cell range) for a line graph or
SPARKBARS(cell range) for a bar graph.
This is pretty raw; like I said, it's just a proof of concept. I figured I'd go ahead and put it out there because I know there's a demand, and I'm hopeful that someone with a little more time to spend on it might be able to polish it up.
Update: This looks way better than my crude prototype.