I have a list in SP2010 and need the user's name to auto-populate in the "Assigned To"
People or Group field whenever s/he submits an new item. Thanks!
This is easily accomplished by using an InfoPath form. You can create a lookup to the user profile sync (syncs with AD): Link
Alternatively, you might be able to create a workflow that copies the user from "Created By" field into "assigned to."