[maxerickson]

For simple queries on OSM data, Overpass Turbo is a nice zero install solution:

http://overpass-turbo.eu/

It uses it's own query language, after that the biggest differences with a local PostGIS would be that it is a shared resource with some limits on query size and the lack of spatial operations (there are a couple simple spatial operations in the Overpass API query language, around an object and inside some boundaries).