File-transfer startup YouSendIt, which allows users to bypass the limits that most email services put on file transfers, announced it raised an extra $15 million in its fourth round of funding on Friday. New investor Adams Street Partners led the round, along with former investors Emergence Capital, Sigma Partners and Alloy Ventures.

YouSendIt allows users to send files sized up to 2 gigabytes through email — though the files aren’t actually transferred via e-mail, but hosted on YouSendIt’s servers and the email recipients are allowed to download them.

But YouSendIt isn’t the only player hosting large files for transfer — RapidShare, MegaUpload and drop.io, among others,