Mostly it is very hard to know if a company or organization is hiring, if they are hiring, it is often even more difficult to know if they need your expertise in their company.
It's amazing sharing this my discovery of listening to career channel of companies and institutions you love on www.zeeders.com. Any time there is an update for the career channel, you will receive it on your wall if you're connected to the career channel. I was able to find out some famous company's zeeders page and connected as I want. Some pages I found are
www.zeeders.com/gtbank
www.zeeders.com/0809ja
www.zeeders.com/nnpc

not sure of these links down here but you can search for the name of the company if you get to your page, sorry it's because I didn't write it down while getting them

www.zeeders.com/mtnnigeria
www.zeeders.com/zenithbank
www.zeeders.com/globacom
www.zeeders.com/neco
www.zeeders.com/airtelnigeria

These are the ones I could get anyway, and all these pages have a career channel that you can listen to for update... You will only recieve updates if they are sent to the public or to the career channel.