Stellar Lumens (XML) is giving away coins on June 27. They will take a snapshot of the bitcoin blockchain on June 26 and allow you to claim your share of XML. 1 BTC of proven balance give you around 617 XML (about 0.009 BTC).
There are some exchanges participating in the giveaway:
Kraken
BTC38
Poloniex
Deribit
Yuanbao
NaoBTC
If your bitcoins are located on any of the above exchanges there is no action for you to take. They will handle the process of automatically crediting your account with the appropriate amount of lumens.
Keep in mind that Poloniex does not count BTC that you lended out. Lending now at 0.15% at poloniex gives you 0.0015 BTC for every 1 BTC of balance. So it is good to pauze your lending and go for the 0.009 BTC in XML. Loans normally are 2 days, so make sure to pauze the lendings on time so not all your balance is tied up in loans and you miss out the opportunity of free XML.