*** More suggestions, updated 18 Aug 2007:
-prices for flights fluctuate dep on season, but expect to pay $1600-1900 for SFO to Europe to Nairobi and back. On off-season (Feb-April), you can find tickets as low as $1200. This is going to be the biggest expense on your trip. Purchase tickets to Nairobi, not directly to Kisumu. i generally call STA Travel, check in with them about pricing trends, and also check out British Air and KLM websites.
Suggestions: try the following online resources for your flight to Nairobi...
http://www.kayak.com - as a clearinghouse for most major online sites (thanks, Kate!)
http://atmtrvl.com/ - a local SF travel agent that Craig Cohen uses, call 415.627.0717
http://www.statravel.com/ - student travel agent, may have special discounts, best to call them for specials (800) 781.4040
Specific airlines that fly to Nairobi:
http://www.britishairways.com
http://www.klm.com
http://www.virgin-atlantic.com
-bag limits are strict from London to Nairobi (one carry-on only, 2 bags at 25kg max each baggage limit) and from Nairobi to Kisumu (if you fly, 20kg max weight for checked bags *total.* they don't weigh your carry on unless it's huge. some airlines will allow you to fudge to 25kg if other people on the plane don't have much stuff). so if you are hauling a lot of stuff, i.e. more than 25kg, you should think about taking a bus instead.
-flights from Nairobi to Kisumu: most people have a half-day or overnight stay in Nairobi and have time to purchase their tickets when they get there. It's really easy to purchase there, and you almost always get a seat. If you prefer to have them in advance (pricing is similar online), you can try purchasing them online with Fly540 or Kenya Air. Their websites seem to work only intermittently, so i tend to purchase the tickets when i'm in Kenya. The flights should cost $40-50 each way on Fly 540. Kenya Air is much more expensive, at about $70-80 each way. There's another small company that also runs a plane shuttle- i forget what it's called, but the prices are comparable to Fly540. For all airlines, there are generally one set of flights in the morning, around 8 am, and one set of flights in the evening, around 6-7 pm.
http://www.fly540.com/
http://www.kenya-airways.com/
-if you need to stay overnight in Nairobi, some recommendations on safe places to stay (take a taxi and don't walk around at night, esp by yourself!):
budget ($5/night) - YMCA hostel: Y.M.C.A. Shauri Moyo Hostel, Ambira Road, PO Box 17073, Nairobi, Kenya, Phone : +254 (2) - 558383, Fax : +254 (2) - 728822
moderate ($40/night): Comfort Hotel, in the city centre: http://www.kenyacomfort.com/
luxury ($100/night): Fairview, out of city centre but gorgeous: http://www.fairviewkenya.com/
-bus from Nairobi to Kisumu: no baggage weight limits, so if you have a lot of stuff, you're up for an 8-hour adventure, don't mind being the only non-Kenyan on the bus, and want to save a bunch of money, you can take the $7 bus from Nairobi to Kisumu. There are a few bus operators, but Easy Coach is the safest and most comfortable (but the slowest). Matatus are much faster and cheaper, but they are more dangerous, and i think the university is discouraging people to take the matatus... personally, i also think that it's even less safe when you are carrying a lot of luggage as thefts are more common on matatus.
At the airport, get an official taxi (with an official taxi number on the window and door) and ask them to take you to the Easy Coach Nairobi station. It's different from the main bus station, which can be hellish chaos. Protect your luggage! Purchase your ticket there and wait for the next bus. Make sure you pee and get food before you board (there will be one or two stops only on the 8-hour ride). The bus may be hot and usually crowded, but since you will be at elevation, it won't be too sticky. Keep your bags on your lap at all times or if you stay awake, keep them overhead and watch them (don't keep them on the floor; they run the risk of getting knifed). Bags in the trunk area of the bus are generally safe because they are monitored by the bus staff, but nothing's ever guaranteed while traveling, regardless of plane or bus. Time on the bus depends on road conditions: 6 to 8+ hours. Try to give Veronica Achieng a call along the way so she knows when you're arriving: pay someone to use their cell phone or call at a rest stop "pay phone" - i.e. pay someone with a special landline to make a call.
Make sure Kimberly Bale knows how you're arriving to Kisumu so she can tell Veronica Achieng where to pick you up! BaleK@globalhealth.ucsf.edu
Update 11/27/07 by Kate
-Airlines that fly from Nairobi to Kisumu are Kenyan Airways (you can buy online in advance, but is more expensive, ~$105 one way). I booked in advance so I could minimize my layover in Nairobi and it worked perfectly - made the 8am flight after getting in on the 6am ft from London. Fly540 is cheaper & has a website, but I haven't tried it and am not sure how well it works. East African and JetLink are the other common options. Both are cheaper (about half the price of Kenya Airways), but I'm not sure about advanced online booking. You can try contacting a local travel agency (Let's Go Travel in Nairobi has been highly recommended) and trying to arrange your ticket through them before you get to Kenya. If you're going to arrange your transfer after arriving in Nairobi, be aware that last month not all flights were going daily and it was a little harder to just walk up and be sure there'd be a seat that day. May have changed by now, though.
- Also, for in-country it appears that if you have >20kg of stuff it's ok as long as it's in 2 bags, neither of which is more than 20kg.