Web-mapping with editing capabilities?

Take a look to OpenLayers for client side, it offers in a simply way all you seems need. As previously suggest to you by Dassouki, take a look to the example page: http://www.openlayers.org/dev/examples/ find for 'edit' For example: http://www.openlayers.org/dev/examples/editingtoolbar.html

For server side I personally bet for OS project, IMO they are incredible good quality and there is nothing they need to envy to proprietary software: GeoServer + PostgreSQL/PostGIS

You might want to try Geoserver in the back-end and use OpenGeo's GXP on the front end. GXP is a client-side javascript library that's built on top of OpenLayers, GeoExt and ExtJS ( now Sencha ). It's supposed to bridge the gap between OpenLayers and full blown web applications. A framework if you will.

Here's a handy guide for getting started with GXP. An example of an app created with GXP is the OpenGeo Suite's GeoExplorer. It's a map viewer, styler and editor.