I don't know how many km rivers I added the last few days in Gabon, Congo-Brazzaville and Cameroon! (... and in other well-mapped corners of world un-emplyed micro-mappers start to map benches and gully covers...!)
Wikipedia is way behind in river decriptions too: no coordinates of river mouths, sometimes no names of affluents and tributaries (but the really huge main rivers)... Best sources for river names is still the UN (for example http://www.un.org/Depts/Cartographic/map/profile/gabon.pdf). Lots to do in Africa - I don't use potlatch for mapping there; josm with landsat has much higher resolution.
And - besides rivers - (nearly) no gpx-tracks to be found in the net! (...was just lucky with finding really good tracks of N2 road(s) in Gabon, Congo and Cameroon ;-)
Now look at some of these never heard river names:
Ogooué basin: Offoué, Ngounié, Mpassa, Ivindo,...
Ivindo basin: Djoua, Liboumba, Mvoung,...
Alima basin: Dziélé, Lékéti,...
Congo basin: Djoué, Sangha, Likouala, Léfini,...
Likouala basin: Mambili, Kouyou, Lékoli, Lengoue,...
...sort of project of the month for me... ;-)