Data appending and cleaning

I've been pretty happy with NetProspex. I've been working with them for about six months and they have a great support team and the data has been accurate. They also have a Marketo Connector which updates data instantly based on form completions.

Please also look at RingLead - they have great deduping and appending abilities. I've heard good things about Reachforce and Netprospex too. Depends on the kinds of leads and countries you operate in though.

Thanks for the quick replies. We only operate in the U.S. and target large companies with at least 10,000 employees. Do you guys know if any of these solutions provide more accurate data for companies of that size?

Any expericne with data.com?

Cody, we target a similar audience and I've been pleased with the data from NetProspex.

We have built Contact Washing Machines (CWMs) for some of our customers. Reachforce, Data.com are good for lead enrichment, whereas Ringlead is good for preventing duplicate records. However, we discovered a common challenge for many marketing ops team, and that is assessing the quality of existing data, and cleaning/enriching that. So, our solution helped teams in data cleansing, normalization and then finally enriching the existing as well as new data. 
Drop me a line at rachitp@grazitti.com and I will share the case study with you for our CWM.