The quickest (though still uncomfortable) way of getting around the country is by sept-place taxi – battered Peugeots that negotiate even the most ragged routes. Slightly cheaper, but infinitely less reliable are the minibuses (Ndiaga Ndiaye or grand car), carrying around 40 people. Vehicles leave from the gare routière when they're full, and they fill up quickest in the morning, before 8am.
Taxi prices are theoretically fixed, though they're steadily increasing as petrol prices rise. There's an extra, negotiable charge for luggage (10% to 20% of the bill).
Cars mourides (large buses, financed by the Mouride brotherhood) connect major towns in Senegal. Book ahead of travel. In Dakar, go to Gare Routière Pompiers, where most sept-places also go from. Arriving in Dakar, sept-places stop at Gare Routière Colobane.