List of public PRPnet and LLRnet servers
(found and updated from here).

PRPnet Servers:

GroupServerSort of search
PrimeGridprpnet.primegrid.com:12000Sophie Germain Prime Search: k·2666666-1
PrimeGridprpnet.primegrid.com:12001121 Prime Search: 121·2n+1, 121·2n-1
PrimeGridprpnet.primegrid.com:12002Factorial Prime Search: n!+1, n!-1
PrimeGridprpnet.primegrid.com:12005Generalized Fermat Prime Search: b32768+1
PrimeGridprpnet.primegrid.com:12003Generalized Fermat Prime Search: b65536+1
PrimeGridprpnet.mine.nu:11002Generalized Fermat Prime Search, b262144-1
PrimeGridprpnet.mine.nu:11001Generalized Fermat Prime Search, b524288-1
PrimeGridprpnet.primegrid.com:12004Generalized Cullen/Woodall Prime Search: n·bn+1, n·bn-1
PrimeGridprpnet.primegrid.com:1200627121 Prime Search: 27·2n+1, 27·2n-1, 121·2n+1
PrimeGridprpnet.primegrid.com:12008Primorial Prime Search: p#+1, p#-1
PrimeGridprpnet.mine.nu:12000Proth Prime Search Extended: 1200 < k < 10000, 300000 > n > 310000
PrimeGridprpnet2.mine.nu:12000Proth Prime Search Extended: 1200 < k < 10000, n < 450000
PrimeGridprpnet.mine.nu:13000Wieferich Prime Search
PrimeGridprpnet.mine.nu:13001Wall-Sun-Sun Prime Search
PrimeGridprpnet.mine.nu:13005Extended Sierpinski Problem: 17 k-values for 2500000 < n < 3000000
PrimeGridprpnet.mine.nu:7171Sierpinski/Riesel Base 5 Project
PrimeGridprpnet.mine.nu:12010Mega Prime Search, 46 k-values < 100, n > 3322000
PrimeGridprpnet.mine.nu:14000Riesel Problem Double Check
PSPwww.psp-project.de:8105Sierpinski/Riesel base 5 Project
PSPwww.psp-project.de:8100Sierpinski base 2 Project
PSPwww.psp-project.de:8101Sierpinski base 2 Project
NPLBwww.noprimeleftbehind.net:2000Riesel Prime Search k·2n-1, 600 < k ≤ 1001, 1000000 < n < 2000000
NPLBwww.noprimeleftbehind.net:9000Riesel Prime Search k·2n-1, 400 < k < 600, 1000000 < n < 2000000
CRUSwww.noprimeleftbehind.net:1400k·bn+/-1, b ≤ 200 with ≤ 5 k's remaining
TPSwww.noprimeleftbehind.net:12000Twin Prime Search 480000 ≤ n ≤ 500000, variable k
TPSwww.noprimeleftbehind.net:13000Twin Prime Search n = 1000000

LLRnet Servers:

GroupServerSort of search
NPLBwww.noprimeleftbehind.net:3500Riesel Prime Search k·2n-1, 6 k's 300 < k < 400, 1000000 < n < 2000000
NPLBwww.noprimeleftbehind.net:7000Riesel Prime Search k·2n-1, 2000 < k < 3000, 350000 < n < 450000
TPSwww.noprimeleftbehind.net:12050Twin Prime Search 480000 ≤ n ≤ 500000, variable k