How do I link to Google Maps with a particular longitude and latitude?

Question

I have a small application that gives the current location: longitude and latitude. Now I have to browse to google maps with the longitude and latitude. Please suggest how I

Answer 1

This schema has changed again (23rd October 2018). See Kushagr's answer for the latest.

This for a map with the marker (via aaronm's comment):

https://www.google.com/maps/?q=-15.623037,18.388672

For an older example (no marker on this one):

https://www.google.com/maps/preview/@-15.623037,18.388672,8z

The oldest format:

http://maps.google.com/maps?ll=-15.623037,18.388672&spn=65.61535,79.013672