There's the SurveyMonkey and Eloqua Integration.
https://www.surveymonkey.com/business/products/enterprise/eloqua-integration-surveys-request-a-demo-lp/Depending on the complexity of the Surveys, the low-complex ones you can easily create in Eloqua.
-5 smileys from happy to unhappy, each with a form submit value ranging from 1-5.
-Creating Forms with questions through radioboxes, dropdowns and textfields.
There is a Survey Monkey interface. We just started using it and there are several option on how you can interface with Survey Monkey. Basically you can send a contact to Survey Monkey and have the survey populate a CDO in Eloqua for analysis.
I have used GetFeedback in the past I can't say enough positive things about them. They have a great integration with Salesforce (being former Salesforce employees they make that an important factor) and they have a much more friendly UI then what I have seen from Survey Monkey (which is the common market leader it seems). GetFeedback seems to come at a premium on the price scale and it seems there price has went up a bit over the years (even more so if you want the Salesforce integration) but was well worth it IMO. Biggest difference I noticed was Getfeedback works on a question by question basis opposed to Survey Monkey which seems to do more of a list of questions per page so that may be a factor on your decision. Also Getfeedback has much more survey question designs then most competitors that I have seen. Makes the questions more fun opposed to the standard plain text style that you see so often. They do not directly integrate with Eloqua but the integration is easy enough if you are working with html based emails since it just required a bit of updates to the links to pull over the Eloqua contact data.