Air France from Paris, France and SN Brussels from Brussels, Belgium. Air Ivoire flies to Conakry regularly from Abidjan en route to Dakar, as does Belvue. Expect to be asked for a "gift" by airport security.
Royal Air Maroc supplies the only direct flight from Montréal to Africa Casablanca, with stopover in N.Y. and many connections from Casa. to Conakry also called Kry and elsewhere.
As of the summer of 2006 it was not safe to cross the Guinean border with Cote d'Ivoire. The rebel group there the MJP has made it a raison d'etre to expel the French military from Cote d'Ivoire.
In 2008 travel between Guinea and Liberia was safe, though time consuming. Hiring a motorcycle is the best option.
Crossing the Guinean border with Senegal is possible but very uncomfortable and requires patience. Inside Guinea, the road between Labe and Koundara is unpaved and very rough. It takes about 8 hours for the whole journey with only minor breakdowns. There are some decent and very cheap places to stay in Koundara. Between Koundara and Diaoube Senegal is a similar journey. The border is relatively hassle free. There is a 20km no man's land between border posts where one only knows they have entered Senegal by the improved quality of the dirt road. It is possible to change your currency at any hour of the night at the border towns on either side of the no man's land. Local transport from Diaoube to Tambacounda and on to Dakar is relatively easy.
Koundara is also the main jump off point for a trip to Guinea-Bissau.