Go to freelancing websites like http://www.odesk.com/ and http://www.elance.com/ and post a job. Make sure you provide any and all details you want the developers to know.
you can go for http://www.exactitsolutions.com
they provide on the spot maintain services, actually they also maintain our three website.
There are many companies out there which do web maintenance but for the cost, you might as well do it yourself.
For a professional web maintainer you can go to http://edynamo.com/
It currently looks bad and I dont like it. Who do i have to contact
