How many queues per interface on a Cisco Switch

It varies based on the line card.  For IOS such as 12.2SX, try "show mls qos queuing interface".

try "show port capabilities"

Dangit! CatOS flashback again.

So what does this tell me?

QOS scheduling:        rx-(2q8t), tx-(1p3q8t)
 
Rx 2 queues and tx 3 queues?

sh int gix/x capabilities

GigabitEthernet3/6
  Dot1x:                 yes
  Model:                 WS-X6724-SFP
  Type:                  1000BaseSX
  Speed:                 1000
  Duplex:                full
  Trunk encap. type:     802.1Q,ISL
  Trunk mode:            on,off,desirable,nonegotiate
  Channel:               yes
  Broadcast suppression: percentage(0-100)
  Flowcontrol:           rx-(off,on,desired),tx-(off,on,desired)
  Membership:            static
  Fast Start:            yes
  QOS scheduling:        rx-(2q8t), tx-(1p3q8t)
  CoS rewrite:           yes
  ToS rewrite:           yes
  Inline power:          no
  SPAN:                  source/destination
  UDLD                   yes
  Link Debounce:         yes
  Link Debounce Time:    yes
  Ports on ASIC:         1-12
  Port-Security:         yes

sh mls qos ?
  aggregate-policer  aggregate-policer keyword
  arp                arp keyword
  ip                 ip keyword
  ipv6               ipv6 keyword
  last               last keyword
  mac                mac keyword
  maps               maps keyword
  module             show entries in module
  mpls               mpls keyword
  protocol           protocol passthrough information
  statistics-export  QOS Statistics export
  |                  Output modifiers
  <cr>