There is apparently a practice among contemporary Jews of giving out blessings on one's birthday. Is there any source for this in the Jewish tradition?
אֲסַפְּרָ֗ה אֶֽ֫ל חֹ֥ק יְֽהוָ֗ה אָמַ֘ר אֵלַ֥י בְּנִ֥י אַ֑תָּה אֲ֝נִ֗י הַיּ֥וֹם יְלִדְתִּֽיךָ׃ שְׁאַ֤ל מִמֶּ֗נִּי וְאֶתְּנָ֣ה ג֭וֹיִם נַחֲלָתֶ֑ךָ וַ֝אֲחֻזָּתְךָ֗ אַפְסֵי־אָֽרֶץ׃
Let me tell of the decree: the LORD said to me, “You are My son, I have fathered you this day. Ask it of Me, and I will make the nations your domain; your estate, the limits of the earth.
I don't know if there's a real mekor (source) for this custom, though those who do, do so based on the face that one's Mazel is empowered on one's birthday.
See Korban Haedah, Yerushalmi Rosh Hashanah 3:8; Chida, Chomas Anach, Iyov 3.
Interestingly, Ohr.edu quotes that the Tiferes Yisrael (Iggeret Tiferet Yisrael 6, Sefer Mayim HaHalacha) "instructed his children that when one of them has a birthday the others should visit and bless him."