Friend of the Followers

Friend of the Followers is an unmarked quest in Fallout: New Vegas.

Detailed walkthrough
When talking for the first time with Julie Farkas about Freeside she will tell you that the Followers of the Apocalypse need a constant supplier for some ingredients used to manufacture medicine items.

For a constant supply talk to James Garret at the Atomic Wrangler and convince him to strike a deal with the Followers. Then report back to Julie, convincing her that the Garrets want to help Freeside in exchange of the Followers' technical skills. After talking to her, report again to James Garret and he will inform you that some of the supplies will be sent immediately. Return again to Julie and gain a huge boost of reputation with them.

Then you also have to spare some of your own Med-X, RadAway or Fixer, 10-15 packs of any should do the trick. Note that you don't need to donate 10-15 of each, but a total of any of them (you can donate only Med-X for example, which is far more common than Fixer and RadAway)

You will know that you successfully completed the quest when the next time you want to donate some supplies, Julie tells you that the item in question is already being mass produced, but she will accept it anyway. After the donation she will offer a discount in medical services and some magazines for you to buy (several Programmer's Digest and Today's Physician, some Lad's Life, Salesman Weekly and one Meeting People) and you will gain more reputation with the Followers as well.