OpenHeatMap takes your standard, not exactly eye-catching spreadsheet data and maps it out across any geographic area, giving you better context and a far more interesting presentation.
Any dataset linked to geographic coordinates (house prices, election results, mortality rates, etc) can be mapped out on OpenHeatMap. OpenHeatMap accepts spreadsheet data from Excel documents, as well as Google Docs formatting. Check out the detailed OpenHeatMap documentation for the specifics on setting up your spreadsheets.
Once you've imported your data, you can tweak the colour sets, heat mapping style and share the heat map by embedding it in your website or sharing a link to it. OpenHeatMap is a free service. Have another heat-mapping service you'd like to share? Let's hear about it in the comments.