[SalesForce] Error: Compile Error: Loop variable must be of type SOBJECT:Account

You cannot assign the standard field Name to the Account lookup. You will need an Account-ID. Something like this:

cc.AccountId = siteObj.Account__c;

The actual reason it failed compilation is because the compiler couldn't detect that it was iterating over a list of sObjects. The same code, with an explicit cast to the proper type, works fine.

That said, if the static method accepts a list or a map as a parameter it makes this code a bit easier to write unit tests against. Passing the trigger collections to the method is not a mandatory practice.

public class LeadBefore {
    public static void UpdateChapterEmailAddress (){

        set<Id> JDRFLocationId = new set<Id>();
        List<Lead> vLstLead = new List<Lead>();

         for(Lead vLead : (List<Lead>)trigger.new)
        {
            if(vLead.JDRF_Location__c != null)
            {
                JDRFLocationId.add(vLead.JDRF_Location__c);
                vLstLead.add(vLead);
            }
        }