Are you confused at where to start your search?? Are you pressed for cash and don't want to shell out $50/year for the Donor Sibling Registry?? Here's a bunch of sites that I recommend as alternatives.
AmFOR Donor Offspring Registry (http://www.amfor.net/DonorOffspring/) -- under the group Americans for Open Records and Bastard Nation, it's the second best registry for US offspring, but is somewhat user-unfriendly to search and find matches....approximately 1,000 offspring/parents and donors listed.....FREE
Donor Offspring Health Registry (http://www.donoroffspringhealth.com/default.aspx?tabId=home) -- new and small registry where you can list donor information as well as health conditions which may or may not have been inherited from the donor....FREE
Donor Offspring Matches (http://www.donoroffspringmatches.com/) -- yet another new and small registry.....FREE
Searching for my sperm donor father (http://www.searchingformyspermdonorfather.org) -- site organized by Tom Ellis featuring several donor offspring's stories and pictures...any adult offspring can be featured, simply email Tom
California Cryobank Sibling Registry (http://www.cryobank.com/sibling_registry2/howtoregister.cfm) -- for offspring/parents (and donors!) of CCB, I don't know much else about it but I don't see a cost involved...must have Internet Explorer to use registry (sorry Mac people!)
Single Mothers By Choice Sibling Registry (http://singlemothersbychoice.com/sibling.html) -- not sure if it's free and it looks like one must actually be a SMC to join??
Australian Donor Conception Registry (http://health.groups.yahoo.com/group/AustralianDonorConceptionRegistry/) -- yahoo group for Aussies....FREE
DonorKind (http://www.donorkind.nl/) -- Dutch DC group/registry....unsure if it costs money or what it's exactly about since I don't read Dutch!
SpenderKinder (http://www.spenderkinder.de) -- German DC group and registry…..new group that is slowly growing ----- DC adults in Germany have to deal with extreme secrecy so this group is cutting edge trying to make people aware
And here's some other resources (some which cost money) for DNA testing and other related databases:
CaBRI: Donor Gamete Archive (http://www.cabrimed.org/donorgametearchive.jsp;jsessionid=6410E1F5D8F023B1E2E1BFB3484AF1A1) -- Donor X and Donor Y Projects for males and females respectively....non-profit organization founded by former donor Kirk Maxey
Donor Y Project -- males submit DNA sample for $25 and get their Y-STR marker values and those are placed in their database and any male sibling or donor can be matched since the Y chromosome passes through generations of males virtually unchanged
Donor X Project -- females must submit their DNA sample as well as their mother's and one other relative from mother's side (ideally a brother - even different donor)...this can cost $50-$75 depending on if a 3rd person is tested or not...the X chromosome that she inherited from her mother can then be determined and by process of elimination which was inherited from the donor - from there female siblings and the donor can be matched if they are on their database
As for finding siblings of opposite sexes, they also do a autosomal (genome-wide) STR test which is $100 per individual
UKDonorLink (http://www.ukdonorlink.org.uk/) -- DNA registry for British offspring and donors to find matches with or without any non-identifying information....£88.13 for DNA test, entry into DonorLink database for life (or as long as registrant wishes) and cross-searches for potential matches on the database at least monthly
Y-Search (http://www.ysearch.org/) -- FREE public Y-DNA database service from FamilyTree DNA....can use Y-STR results from FamilyTree, CaBRI, and any other testing company which uses the Y chromosome for genealogical testing, can find people who may not be the donor but like FamilyTree could be relatives which carry the same surname (see How to identify your anonymous sperm donor) ----- for MALES only!!
FamilyTree DNA (http://www.familytreedna.com/) -- largest DNA and genealogical database in the world.....$149 for Y12-STR marker test and $259 for Y37-STR marker test -- MALES ONLY.....loads of other cool tests, but can get quite pricey
Genetic Testing Laboratories (http://www.gtldna.com/) -- $99 paternity tests (have a sale $89 test for limited time!) and $150 full/half-sibling tests....keep DNA samples/records for 6 months for additional testing of another potential match ---- cheap, reliable, and fully accredited