We are contemplating a complete UI redesign for our flagship product, acupuncture software called AcuGraph (http://www.acugraph.com). Central to the functionality of this software is drawing lots of different kinds of graphs - bar, pie, etc. Through the first 4 iterations of this project and over the last 10 years, I’ve hand-coded all the graph drawing logic. While the results are ok, we are looking for something with more visual appeal.
There are plenty of awesome graphing libraries out there for other environments, some that product really outstanding results: jPGraph, pChart, Google Chart API, etc. for example.
In terms of DIY then you can use google API from within xojo, I do this for one app but relies on internet connection, as you need htmlviewer (xojo generating the HTML code internally) - though it gives very nice results and is extremely powerful . If you have MS Excel available then generating data within xojo and viewing graphical output in Excel is easy enough (good for reporting and printing which is why I use this option as xojo output is not that easy to master).
There is a post earlier announcing a graphical package which maybe useful
However, having said all this, I ended up writing my own routines for 2D/3D bars and charts plus scatter/line to actually get what I wanted and not what other packages dictated - it turned out trivially easy much to my surprise.