I assume to buy. Next lot of houses should be ready by June 2011. Most of them have been booked. Booking is done by paying sh 1,000 for a form, filling it and submitting it with a deposit of at least 10% of the purchase price. Naturally those with higher deposits stand a better chance of getting allocated.
Should you wish for more details call in at the TPS office 4th floor Social Security House Block A.
If you want to rent just take a walk to the estate management office. They usually have details of purchasers who wish to rent. NSSF doesn't rent out itself, but just sells.

You can also try NHC Langata, good prices and location. Very impartial

These houses sell for about 4.8M and rent out at about 20K per month. The yield is therefore a very low 5%.

@Innovator, go to NHC offices behind Co-op bank headquarters 7th floor, the usual 10% deposit and 200kshs for the application form, houses between 4.5m & 4.9m. As of last year Dec they were not taking any new applications and September this year the allocations were done for phase iv, so i don't think there are any left unsold however they could be building a new phase try your luck.

For Information:
The next phase is on sale. Today's standard, Home & away page 10. 3 b/r flat now at 6.1m