[ephermata]

While none of these are exactly the same as Exec, they do let you hire people remotely to do things.

http://www.taskrabbit.com (see also API at http://taskrabbit.github.com)

http://www.zaarly.com http://www.gigwalk.com http://www.gigboard.com

Exec differentiates on up front pricing ($25/hr), fast fulfillment (within 10 minutes), and on positioning toward executive assistant services. There's an interesting comparison table to be made with columns like "number of active workers," "geographic regions covered," "pricing model," "top 5 tasks" etc.

There's also craigslist, of course, which is highly liquid and has high reach. Craigslist doesn't have a great experience, though, for hiring people.