Some information collections, such as calendar data (event dates), or geographical data (event locations), are often displayed as textual information, although they do have a 'natural' graphical representation - as a calendar, in the case of dates, or on a map, for locations.
It is now relatively easy to create online maps and calendars that can be embedded in your own web pages, captured and converted to document formats that preserve layout information (such as the PDF document type) or printed off directly from the web browser or desktop application.
For example, here is a map displaying all the Open University regional offices (click on a logo/marker to see information about each one):
View Larger Map
(The map and the overlay markers are both pulled into the page as 'live' information.)
Calendars can be embedded in web pages too, typically using either a monthly, weekly or even daily calendar style, or as a list ('agenda' style).
It is even possible to take data from a calendar, and use the location information to plot the calendar events on a map, as this blog post describes: Displaying Google Calendar Events on a Map.
Plotting Map Data
One of the easiest ways to plot location data onto a map is to add it as an overlay. That is, as a visualisation layer that sits on top of the actual map image layer.
The data is pulled in to the map using a data format that can encode geographical location information, such as the latitude and longitude of a point, and maybe its altitude above sea level.
One standard that has come to the fore in recent times is KML, once known as the "Keyhole Markup Language" and originally designed for the Keyhole 3D geographical visualisation tool that has become Google Earth. KML is capable of representing lines and complex polygons (that is, complex 2D and 3D shape overlays), as well as adding image overlays and carrying payloads (such as HTML and embedded video players) into geo-visualisation tools.
At the other extreme, geoRSS is a lightweight, emergent standard that extends the RSS syndication protocol with latitude and longitude co-ordinate. Many online mapping tools accept geoRSS, which means that web publishers who publish their content via RSS feeds already can also push that content into a map based display, if appropriate.
A good example of a site that supports this is flickr, the online photo sharing site, which allows users to add location metadata to their photographs describing the location they were taken. This information can then be exposed via geoRSS, or the flickr API, and used to create displays such as flickrvision, which plots recently uploaded photos on a map.
A simple way of creating your own map overlays is to use a service such as Google MyMaps.