The site SearchingForMySpermDonorFather.org was created by Tom and is a registry with a list of donor-offspring looking for their biological parents and sperm donors looking for their biological children. SearchingForMySpermDonorFather.org is no longer open to new members.
Other recommended ways of searching
DonorChildren is a free and active register and we recommend that any donor-conceived people or donors register there.
We strongly recommend that every donor-conceived male and every sperm donor register for a Y-chromosome test with Family Tree DNA.com.
The Donor Sibling Registry is an international registry of sperm donors and donor offspring, and it is very useful to register there.