As the full extent of the disaster has begun to unfold, residents also posted pictures of those missing on Facebook, with hundreds of messages and pleas for information about friends and relatives.
Solidarity groups also sprang up on the site, with the Haitian diaspora mobilising to support their homeland with financial help and information.
Twitter was also deluged with messages on ways to "Help Haiti", which was one of the top 10 most popular topics on the site.
Relief efforts included sending money by text message to the American Red Cross and to Yele.org, a charity set up by Haitian-born singer Wyclef Jean.
However, the US Federal Bureau of Investigation (FBI) warned potential donors to be on the lookout for fraud schemes.
"The FBI today reminds internet users who receive appeals to donate money in the aftermath of Tuesday's earthquake in Haiti to apply a critical eye and do their due diligence before responding to those requests," the FBI said in a statement.
"Past tragedies and natural disasters have prompted individuals with criminal intent to solicit contributions purportedly for a charitable organisation and/or a good cause," it said.