Every time I want to do conversion, I need to get into the console to run proj.4. Is there any online tools for converting coordinates between different EPSG?
This one's pretty handy: http://cs2cs.mygeodata.eu/
Also useful for batch conversions.
To do a one-off projection, I usually use the geometry service on our ArcGIS Server's REST endpoint.
You could also use ArcGIS Online's Rest Endpoint, which is available here.
Here is a sample which shows how you can project from 4326 to 3857.
Please note that you need to comply with their Terms & Conditions.