Plotting GPS Data : Multiple locations

i need help for plotting multiple location data on a digital map on
real time basis.
please suggest GIS platform and a way to do it

Depends on what your requirement is,

* you can use Google Maps API to plot your real-time GPS data on a
google maps interface, this is the most popular way. Alternatives are
Yahoo Maps API and Virtual Earth API.
* Use open-source alternatives such as OpenLayers, to do the same
thing as above. Coding language is Javascript for both GMaps and
Openlayers
* If you know KML, you can write a NetworkLink to display the data on
Google Earth

For all the above applications, you'll need to store your data in some
sort of database first. If you want to do some spatial queries, use a
spatially enabled database like, Oracle Spatial or Postgresql
( free ).

-Ujaval
http://spatialthoughts.com