Have driven a few times along the horse race track many years ago, but in general Waregem has not directly a reputation as a tourist destination, so never had a closer look there. Hopefully the local TI can tell you more. Local football club SV Zulte-Waregem plays for many years at the highest level in Belgium, maybe worth visiting a football game.
You can use Waregem as a base for daytrips to the well-known places like Bruges, Ghent, Antwerp and even Lille in France. Nearby Oudenaerde has a lovely main square and a bicycle race museum and I think former world champion Freddy Martens still works there as a host. Tournai east of Lille, but still in Belgium is worth considering a visit too. http://crvv.be/exhibitions/?lang=en
Closer to Ghent, the renaissance castle of Ooidonk is really lovely, but usually only open for a visit on Sundays till 15 September, the garden every day of the week except Monday and Tuesday morning. Have no idea how to reach the place easily by public transport. http://ooidonk.be/en/visit
Kruishoutem a few km east of Waregem is the home of Peter Goossens, one of Belgiums most reknown chefs de cuisine. In case budget is not a problem…..but book well in advance..
