Trails

Those websites have several tracks from basically everywhere.
Check the icons to find out what kind of tracks they have. Most of them also offer to download the tracks as .gpx

Hiking

MTB

Climbing

Riding

Biking

Kayaking

Winter Sports

Offroad

EveryTrail

Database with more than 50,000 tracks from basically everywhere.

GPStracks

Dutch database with more than 2,500 tracks mainly from the Netherlands, Belgium, Germany and France.

wikiloc

Nice database with more than 50,000 Tracks from all over the world

GPSies

Biggest database (we know of) with more than 90,000 tracks of more than 100 countries.

AlpinTouren

Database with more than 7,000 trails (not all of the with gps tracks). The site is only in German available.

Turbolince

Nice website with MTB tracks mainly from the Alps, but most description are in Italian

gpsbiketracks

Database with more than 100 bike-tracks, mainly from Belgium. The site is in Dutch.

Rutas y Viajes

Spanish trails database with more than 1000 trails. The site is in spanish only.

Walking away

Small German website with long distance hiking trails and some smaller hiking trails. -with gpx tracks.

GPS-Tracks

Database with more than 5,000 tracks

EIFEL-GPS

Nice website with more than 100 trails in the Eifel. Site is available in German only

GPS-Touren

Database with more than 800 tracks, mainly from within Switzerland. The site is in German.

Wanderkompass

German website with long distance hiking trails which are divided into 10-20km portions -good for daytrips too

Trace GPS

Nice big Database with more than 4,000 Tracks -only from France

trailpeak

Nice big Database with more than 10,000 Tracks with a focus on Northamerica

singletracks

Database with more than 2,500 MTB Trails (focus on the US and Canada).

GPS Tour

Database with more than 17,000 tracks.

outdooractive

Quite new german database with 3,000 tracks.

Kompass

Suggestions for more than 1,000 trips for any acivity -in german only.

Bikemap

More than 80.000 biketracks from almost everywhere. Nice mapsearch!

Wandermap

Nice mapbased database with more than 2000 hikingtrips