If you want to see your .gpx files (from your Garmin or tracklogger) on an OpenStreetMap without uploading them first to osm then you can use GpxToSlippyMap.
The program just adapts the .html file from the Openlayers Track example: http://wiki.openstreetmap.org/wiki/Openlayers_Track_example
Download a (windows only) executable here: http://tinyurl.com/yl9a7hp
The program accepts .plt, .kml (f.i. eurasia.kml, america.kml) and .poly (CloudMade) files too.
Also multiple files can be dropped. For every file there will be a layer.
Reducing of number of points in a track. For if a track has so many points that browsers get slow.
Support for tracks in .fit files. (Tested with those from an Edge 500). Converts .fit to .gpx. (Well partially. (Only lat,lon))
Version 10 feb 2011:
Support for unicode file names.
Osmarender tileserver is down. You need to update or remove following two lines from the produced html file:
layerTilesAtHome = new OpenLayers.Layer.OSM.Osmarender(“Osmarender”);