Projects with apps for Android listed below. Post up if you know of others.
The following projects currently support Android: ARM / NEON unless stated.
Albert
Asteroids@home
Collatz ( ARM and x86 )
Einstein@Home
Enigma@home
Milkyway@home 
Moowrapper
Ralph
Rosetta 
Seti@Home
Seti@Home Beta ( ARM and x86 )
Citizen Science Grid SubsetSum@Home Sum Calculator 
theSkyNet POGS 
Universe@home ( ARM on Linux )
World Community Grid (  Fight Aids app  Ebola app Zika app )
WUProp@home    ( ARM and x86 ) 
Yoho@home ( YoYo@home if you prefer  :pirate: )
As the info in this post is ancient I have updated using the excellent information supplied by Dirk Broer.
Android Boinc Projects
| PROJECT | App STATUS | Android/32 ARM    Application | Android/64 ARM Application | Android/32 x86 Application | Android/32 x64 Application | Android/32 MIPS Application | 
|---|
| Albert@home | Active | Binary Radio Pulsar Search 1.44 (NEON)Binary Radio Pulsar Search 1.46 (NEONPIE)
 | None | None | None | None | 
| Asteroids@home | Active | Period Search Application 102.11 (arm_android_non_pie)Period Search Application 102.12 (arm_android_pie)
 | None | None | None | None | 
| Citizen Science Grid | Inactive | SubsetSum@Home Sum Calculator (up to Android 4.4 (non-PIE))
 | None | None | None | None | 
| Collatz Conjecture | Active | Micro Collatz Conjecture 6.00 (android_arm_non_pie)Micro Collatz Conjecture 6.01 (android_arm_pie)Collatz Sieve 1.01 (android_arm_non_pie)Collatz Sieve 1.01 (android_arm_pie)
 | None | Micro Collatz Conjecture 6.00
 | None | Micro Collatz Conjecture 6.00
 | 
| PROJECT | App STATUS | Android/32 ARM    Application | Android/64 ARM Application | Android/32 x86 Application | Android/32 x64 Application | Android/32 MIPS Application | 
|---|
| Einstein@Home | Active | Binary Radio Pulsar Search (Arecibo) 1.43 (NEON)Binary Radio Pulsar Search (Arecibo) 1.43 (VFP)Binary Radio Pulsar Search (Arecibo) 1.46 (ASIMDPIE)Binary Radio Pulsar Search (Arecibo) 1.46 (NEONPIE)
 | None | None | None | None | 
| Enigma@home | Inactive | Enigma 0.76b (up to Android 4.4 (non-PIE))
 | None | None | None | None | 
| GPUGrid | Inactive | inactive / discontinued ?
 | None | None | None | None | 
| Grid computing center | Active | Monkeys v1 (NCI) - Generator/1 seed 19.00 (android_arm_non_pie)(nci)Monkeys v1 (NCI) - Generator/1 seed 20.00 (android_arm_pie)(nci)Monkeys v2 (NCI) - Seeker/1 seed 11.00 (android_arm_non_pie)(nci)Monkeys v2 (NCI) - Seeker/1 seed 11.00 (android_arm_pie)(nci)Monkeys v3 (NCI) - Generator/Word seed 2.00 (nci)Monkeys v4 (NCI) - Seeker/Word seed 8.00 (nci)
 | Monkeys v1 (NCI) - Generator/1 seed 19.00 (android_arm64_pie)Monkeys v2 (NCI) - Seeker/1 seed 9.00 (android_arm64_pie)(nci)Monkeys v3 (NCI) - Generator/Word seed 2.00 (android_arm64_pie)Monkeys v4 (NCI) - Seeker/Word seed 6.00 (android_arm64_pie)
 | None | None | None | 
| PROJECT | App STATUS | Android/32 ARM    Application | Android/64 ARM Application | Android/32 x86 Application | Android/32 x64 Application | Android/32 MIPS Application | 
|---|
| LHC@Home | Active |  | sixtracktest (beta test) 46.15 (sse2)
 | None | None | None | 
| Moo! Wrapper | Active | Distributed.net Client 1.04 (arm_android_non_pie)Distributed.net Client 1.04 (arm_android_pie)
 | None | None | None | None | 
| Quake Catcher Network | Inactive |  | None | None | None | None | 
| Quake-Catcher Network (Taiwan) | Active |  | None | None | None | None | 
| Quake-Catcher Network EMSC / CSEM QCN QCN | Active | Sensor Monitoring Program 7.43 (nci)
 | None | None | None | None | 
| Quake Catcher Network Continual | Inactive |  | None | None | None | None | 
| Quake-Catcher Network Continual (Taiwan) | Inactive |  | None | None | None | None | 
| Quake-Catcher Network Continual EMSC / SCEM QCN | Active | Continual Monitoring Program 7.43 (nci)
 | None | None | None | None | 
| Ralph@home | Active | Rosetta Mini for Android 3.83
 | None | None | None | None | 
| Rosetta@home | Active | Rosetta Mini for Android 3.83
 | None | None | None | None | 
| PROJECT | App STATUS | Android/32 ARM Application | Android/64 ARM Application | Android/32 x86 Application | Android/32 x64 Application | Android/32 MIPS Application | 
|---|
| Seti@Home | Active | SETI@home v8.00 (armv6-neon)SETI@home v8.00 (armv6-neon-nopie)SETI@home v8.00 (armv6-vfp)SETI@home v8.00 (armv6-vfp-nopie)SETI@home v8.00 (armv7-neon)SETI@home v8.00 (armv7-neon-nopie)SETI@home v8.00 (armv7-vfpv3)SETI@home v8.00 (armv7-vfpv3-nopie)SETI@home v8.00 (armv7-vfpv3d16)SETI@home v8.00 (armv7-vfpv3d16-nopie)SETI@home v8.00 (armv7-vfpv4)SETI@home v8.00 (armv7-vfpv4-nopie)
 | SETI@home v8.00 (arm64-neon)SETI@home v8.00 (arm64-vfpv4)SETI@home v8.01
 | SETI@home v8.00 (nopie)SETI@home v8.00 (pie)
 | None | None | 
| Seti@Home Beta | Active | SETI@home v8.01 (armv6-neon)SETI@home v8.01 (armv6-neon-nopie)SETI@home v8.01 (armv6-vfp)SETI@home v8.01 (armv6-vfp-nopie)SETI@home v8.01 (armv7-neon)SETI@home v8.01 (armv7-neon-nopie)SETI@home v8.01 (armv7-vfpv3)SETI@home v8.01 (armv7-vfpv3-nopie)SETI@home v8.01 (armv7-vfpv3d16)SETI@home v8.01 (armv7-vfpv3d16-nopie)SETI@home v8.01 (armv7-vfpv4)SETI@home v8.01 (armv7-vfpv4-nopie)
 | SETI@home v8.00SETI@home v8.00 (api24)SETI@home v8.01 (arm64-neon)SETI@home v8.01 (arm64-vfpv4)
 | SETI@home v8.01 (nopie)SETI@home v8.01 (pie)
 | None | None | 
[/tbody]
| PROJECT | App STATUS | Android/32 ARM    Application | Android/64 ARM Application | Android/32 x86 Application | Android/32 x64 Application | Android/32 MIPS Application | 
|---|
| The SkyNetPOGS | Active | fitsedwrapper 4.02 (android_arm_non_pie)fitsedwrapper 4.02 (android_arm_non_pie_old_client)fitsedwrapper 4.02 (android_arm_pie)fitsedwrapper 4.02 (android_arm_pie_old_client)
 | None | None | None | None | 
| Universe@home | Active | Universe BHspin v2 0.01 (android_arm_pie)
 |  | None | None | None | 
| World Community Grid | Active | Fight Aids appEbola appZika app
 | None | None | None | None | 
| WUProp@home | Active | Data collect version 4.20 (nci)Data collect version 5.03 (android_arm_non_pie)Data collect version 5.07 (android_arm_pie)
 | None | Data collect version 5.03 (android_arm_non_pie)Data collect version 5.03 (android_arm_pie)
 | None | None | 
| Yoyo@home | Active |  | None | None | None | None | 
[/tbody]