Some of them for AAA (Authentication, Authorization and Accounting in the IMS). First, for Authentication and Authorization:
Cx interface: specified between either an I-CSCF or an S-CSCF and an HSS.
Dx interface: specified between either an I-CSCF or an S-CSCF and an SLF.
Sh interface: specified between either an SIP-AS or an OSA-SCS and an HSS.
Zh interface: specified between an HSS and a BSF.
Zn interface: specified between a BSF and a NAF.
Now, for Accounting, Policy and Charging Control in the IMS:
Rx interface: specified between an AF and a PCRF.
Gx interface: specified between a PCRF and a PCEF.
Gz interface: specified between the PCEF and the OFCS
Ro interface: specified between the OCF and any of the following: IMS-GWF, SIP-AS, MRFC or GGSN.
Rf interface: specified between the CDF and any of the following: MRFC, MGCF, BGCF, SIP-AS, P-CSCF, I-CSCF or S-CSCF.
Between LTE’s EPC and IMS:
S6a interface: specified between an MME and the HSS.
SLs interface: specified between an MME and the E-SMLC
SLg interface: specified between an MME and a GMLC.
SLh interface: specified between an HSS and a GMLC.
S13 interface: specified between an MME and an EIR.
Acronyms used for entities involved in Diameter based interfaces described upwards (in order of appearance):
I-CSCF and S-CSCF: Interrogating and Serving Call Session Control Function.
HSS: Home Subscriber Server.
SLF: Subscriber Location Function
SIP-AS: Session Initiation Protocol - Application Server.
OSA-SCS: Open Service Access – Service Capability Server.
BSF: Bootstrapping Server Functionality.
NAF: Network Application Function (operator-controlled functionality)
AF: Application Function (e.g.: SIP-AS, P-CSCF, etc.).
PCRF: Policy and Charging Rules Function.
P-CSCF: Proxy Call Session Control Function.
PCEF: Policy and Charging Enforcement Function
OCF: Online Charging Function.
IMS-GWF: IMS Gateway Function.
MRFC: Media Resource Function Controller.
GGSN: GPRS Gateway Support Node.
OFCS: Offline Charging System.
MGCF: Media Gateway Control Function.
BGCF: Breakout Gateway Control Functions.
EPC: Evolved Packet Core.
MME: Mobility Management Entity.
E-SMLC: Evolved Serving Mobile Location Center.
GMLC: Gateway Mobile Location Center.
EIR: Equipment Identity Register.
For more, better look at 3GPP TS 23.002 and its internal references regarding Diameter interfaces, i.e.:
3GPP TS 29.272: "Evolved Packet System (EPS); Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocol".
3GPP TS 29.173: "Location Services (LCS); Diameter-based SLh interface for Control Plane LCS".
3GPP TS 29.336: "Home Subscriber Server (HSS) diameter interfaces for interworking with packet data networks and applications".
3GPP TS 29.337: "Diameter based T4 Interface for communications with packet data networks and applications".
3GPP TS 29.338: "Diameter based protocols to support of SMS capable MMEs".
IETF RFC 4006: "Diameter Credit-Control Application".