WordPress is the most popular CMS in the world to manage your website, but it needs to be done right. Depending on the level of services you're looking for, I have different personal recommendations to make for you.
Over 50,000 USD/CHFEnterprise
At Human Made, we have a proven team of 50+ people. We're not only a WordPress.com VIP Partner, but also deeply embedded in the WordPress community with contributions on all fronts. We have solved numerous challenges for large-scale organisations and high-profile clients. Beyond ongoing development work, we also offer thorough code reviews and large-scale migrations . We'd love to talk about your project, just send me an e-mail.
3,000 to 50,000 USD/CHFSmall to Medium Business
If you're not quite enterprise yet and looking for a complete site-build, use Toptal. They're the premier service for connecting clients to developers and designers. If I had to hire someone for an application unknown to us, I'd do it here. Unlike Elance or oDesk, Toptal is completely inserted in the process and personally there to help guide you. Fill out the form to see who's available or just e-mail me to introduce you.
Under 3,000 USD/CHFSmall changes
Finally and no matter how small, check Codeable for the few odds and ends you need done. Toptal is still a great choice here, but if you only have small changes Codeable is a good way to go.