There is no internal flight network in Sierra Leone.
Sierra Leone's compact size means that distances can be covered fairly easily by bike. The rate of road accidents in Sierra Leone is high, and driving erratic, so it's best to avoid major tarmac roads, where most of these incidents occur. Panniers are a must-have, and you should carry emergency food and water supplies when travelling in more remote areas, as well as any equipment you'll need in case of a breakdown.
Pam-pahs operate to several towns, most notably between Mattru Jong and Bonthe.
Speedboat hire costs from US$600 per day while slower pam-pahs (which hold up to 20 people) cost around US$300. In Freetown, enquire at the Freetown Aqua Sports Club, Government Wharf, Kissy Terminal and the Conservation Society.
Car & Motorcycle
Car hire is expensive (starting at around US$100 a day for a car with a driver in Freetown, and at least US$150 to head upcountry, not including the driver's expenses), but don't choose a company only on the price; ask about the terms too. Visit Sierra Leone and IPC Travel both hire reliable vehicles with drivers. Another good company is Sierra Leone Car Hire.
You could also just charter ('chatah') a taxi. In Freetown, you can usually negotiate an hourly rate of Le30,000 per hour.
Bush taxis and poda-podas (minibuses) link most towns; however, except for departures to and from Freetown and between Bo and Kenema, you'll find that traffic is usually pretty sparse, especially on Sunday. Buses will usually cost a little less, but they are slower.
Sierra Leone's national railway ceased operation in the 1970s.