I just found a nice web interface for converting Shapefiles to geoJSON, the preferred format of vector geodata on the web. And yes, you can also convert back from geoJSON to ESRI Shapefile.
Check it out: http://ogre.adc4gis.com/
So if you need to do any geodata conversions or preprocessing, you should have a look at it. You’ll find plenty of tutorial on the web.
And by the way, the OGRE Interface is open source and you can build your own web converter if have some time left and you don’t know anything better to do.