A commenter named Jon asked, "When Paul speaks of the giving Macedonian churches in II Cor 8,is the church in Thessolonica the one he is speaking specifically about?" Jon may or may not know that I've long had a fondness for the Story of Thessalonica. But that doesn't mean I can play favorites this time. Anyway, here's my answer.
Paul's thankfulness in his letter to the Philippians includes mentioning a number of times they provided for his needs. It must have helped Philippi (the church) to have Lydia there. As a seller of purple (dye/cloth?) Lydia had financial means that were probably uncommon in most early churches. However modest, her wealth must have been one major reason for Philippi's custom of sending Paul financial gifts. And if not strictly Lydia, it still had to be some more than others. The '80/20 rule' in ancient socio-economics was closer to 95/5.
Thus, Philippi was one very giving church that we know of for certain. If Paul wrote any thank you letters to Berea or Thessalonica, we don't know about them. However, just like Paul thanked the whole church in Philippi for the gift certain saints may not have contributed to, Paul gave credit to Macedonia as a group, instead of mentioning which church(es?) gave more than the others.
Therefore, Thessalonica and/or Berea most likely did make some contribution to the collection in 2 Cor 8, but it's most likely that Philippi did the lion's share of the giving, as usual.