Mathias Brandewinder has recently created a series where he walks through how to create a VSTO solution for Excel 2007 using VSTO 3.0 and C#. I find the series to be good and of interest for everyone that is interested of VSTO & Excel.
For more information please see: Excel 2007 VSTO add-in: table of contents
PS. Mathias use an interesting free software for his site which is also worth to check out.