ABAKA
Prague's districts explained.
http://www.abaka.com/Czech/Praha_districts.shtml

eTravel.cz
Prague, district by district.
http://guide.travel.cz/12

Lonely Planet
Highlights the major tourist attractions in each of the city's neighbourhoods.
http://www.lonelyplanet.com/destinations/europe/prague/attractions.htm

Property in Prague
A neighbourhood guide that is aimed at house hunters, but is useful to all.
http://www.itlphoenix.com/PragueDistricts.htm http://www.itlphoenix.com/PragueDistricts.htm

Rough Guides
The section on Prague on this website includes detailed descriptions of the city's main neighbourhoods.
http://travel.roughguides.com/roughguides.html