1. Jeon So Mi
The #1 girl in 'Produce 101' hasn't officially debuted yet, but she's been keeping super busy through various CFs, endorsement deals, variety shows, and even songs through the KBS variety show 'Unnies' as well as a duet with Eric Nam. JYP Entertainment had said they weren't in a rush to debut her as she's still so young, and with Stray Kids coming out soon, it may be some time until she officially debuts. However, she's still staying busy so fans can still see her all the time.
Kim Se Jung, Kang Mi Na, and Kim Na Young all debuted with their label Jellyfish Entertainment's new girl group Gugudan. Kim Se Jung has had a solo song that won #1 and even acted. Kang Mi Na had her subunit 'Gugudan 5959', and is also preparing to debut as an actress.
3. Weki Meki
Weki Meki actually has 4 girls that were in 'Produce 101'. Choi Yoo Jung and Kim Do Yeon are the ones everyone knows because they made it into IOI. However, Elly (Jung Hae Rim) was also part of 'Produce 101' under Fantagio Entertainment, and Sei was also part of 'Produce 101', but she was under LOUDERS Entertainment.
4. Kim Chung Ha
Kim Chung Ha made an incredibly successful solo debut with 'Why Don't You Know'. Chart-wise, she's actually performed the best out of all the IOI girls (minus Kim Se Jung's solo song) and ranked decently for a very long time. Hopefully she'll come back soon!
5. Kim So Hye
Kim So Hye has been mostly on variety shows, CFs, and doing special appearances all across the board. She hasn't quite been acting very much, but is still staying active and meeting her fans through various events. As Kim So Hye was an actress-in-training, hopefully we'll get to see her in more than just event appearances soon.
Seven out of the ten PRISTIN members are from 'Produce 101' - Nayoung and Kyulkyung were in IOI, and the rest (Xiyeon, Roa, Yuha, Eunwoo, Rena) all ranked high in the show. The girls had a successful debut with the highly addicting "Wee Woo", and continued to get stuck in heads with comeback song "We Like".
DIA has Jung Chae Yeon and Ki Hee Hyun (who used to go by Cathy before her 'Produce 101' appearance). Jung Chae Yeon has been active all over the place, including highly successful dramas, and Ki Hee Hyun made her talents known through 'Unpretty Rapstar' as well. Two of the members will be taking a break from DIA to go on KBS' idol-rebooting show 'The Unit'.
8. Cosmic Girls
Yeonjung, IOI's power vocalist, joined Starship Entertainment's existing group Cosmic Girls to add to their vocal power. She's currently the main vocal of the 13-member girl group and still amazes with her clear, powerful voice. She's been compared to other soloists such as Taeyeon.
9. Han Hye Ri
Han Hye Ri had a unit debut with project group IBI also made up of 'Produce 101' members. After, she was supposed to debut under Star Empire as a member of OMZM, but she ultimately left the group after plans fell apart. She is currently without a label.
After IBI, Lee Soo Hyun (and Lee Hae In, but we'll get to her later on this list) left SS Entertainment to join HYWY Entertainment. It was revealed earlier this year that she would be debuting under DAYDAY, a 5-member girl group. However, it's been a while since anything has been updated about the girls, so hopefully things are still going well.
11. Kim So Hee
It's pretty surprising that Kim So Hee, a Music Works trainee, hasn't officially debuted yet as a soloist. However, she has been staying active through IBI and then through 'Idol Drama Operations Team'.
Yoon Chae Kyung joined DSP Entertainment's already existing April. While not wildly successful, April has been making a steady name for themselves with their clear, innocent image, and Chaekyung is a perfect fit for the group.
13. Lee Hae In
Lee Hae In has had a really rough career - after 'Produce 101', she and fellow SS Entertainment trainee Lee Soo Hyun left the label. However, mistreatment at the label caused her to be diagnosed with a panic disorder which ultimately resulted in her leaving her new label and the group she was supposed to be debut with. She then came out to 'Idol School' but ultimately did not make the cut there either, just barely missing the debut cut off. Here's to hoping her road is better paved from now on.
14. LOEN Girls
Park So Yeon and Lee Soo Min will both be debuting soon under LOEN Entertainment. Lee Soo Min was originally part of Fantagio Entertainment but left, and after her appearance on 'K-Pop Star 6', was signed onto LOEN Entertainment. The girls, along with some other LOEN trainees, are being called 'LOEN Girls' as they prepare for official debut.
15. Jeon So Yeon
She appeared on 'Unpretty Rapstar' after 'Produce 101', and then also recently showed herself during 'Produce 101' season 2 to give advice to label hoobaes Lai Kwanlin and Yu Seon Ho. She has signed an exclusive contract with Cube Entertainment and was supposed to debut in 2017, so we'll see if she actually debuts in the couple of months that are left.
16. Kang Si Ra
Kang Si Ra debuted in early 2017 and had an OST right after her debut, but has been mostly under the radar since then. She appeared back for a flash in May when her official fancafe was founded, but hasn't been up to much since.
17. Ng Sze Kai
The Hong Kong pop star went back to her group AS1 after the end of 'Produce 101', but since then has left and has been doing her own thing. She's also recently in the summer released a solo single, and is an actress hopeful.
Chanmi didn't appear in 'Idol School', but it's been reported that her (and the other trainees at her label) will be on 'Mix Nine'. Hopefully things work out better for his this time around.
19. Hwang In Sun
Auntie Hwang has returned back to being a solo singer and has put out various singles since 'Produce 101' such as 'Emoticon' and 'Hwang Ya'. She also participated in 'Society Game', and has been pretty active even after the end of the show.
Out of the five girls, only Sora wasn't a 'Produce 101' contestant. However, sadly enough the group has pretty much disbanded with Hyungeun and Sora leaving the group. There's always a possibility that new members can join, so we'll see what the girls do next.
21. Kim Ju Na
The vocalist debuted in September 2016 after 'Produce 101', but hasn't been active much after her debut song. (Perhaps it was an error to call a song in September 'Summer Dream'..)
One of the top visuals of 'Produce 101' (voted by the girls themselves), Eunbin went on to join Cube Entertainment's already existing group CLC. CLC is also starting to steadily make a name for themselves with hits such as 'Hobgoblin' and their latest 'Where Are You?'.