We have had real world experience with all of the following technologies. Not listed here? We'll take it on regardless.
Virtualization:
Docker, ECS, Xen, VMWare ESX and ESXi, KVM, Vagrant, Eucalyptus, and Virtual Box
Cloud:
Amazon AWS including EC2, CloudWatch, Autoscaling, ELB, ALB, Athena, RDS, Route53, OpsWorks, S3, EMR, SNS, SQS, VPC, Glacier, IAM, Kinesis, Redshift, DynamoDB, CloudFormation, CloudTrail, Config, Elastic Transcoder, SES, EFS, Cloudfront, Lambda, Inspector, and ElastiCache
App stacks:
Apache, nginx, Terracotta, Tomcat, JBoss, Smartfox, Magento, Kibana, Joomla, PHP, jQuery, CSS, and Java
Toolsets:
Nagios, Chef, Ruby, Cacti, Splunk, AppDynamics, Jira, Logstash, Sensu, New Relic, Maven, Bamboo, Jenkins/Hudson, Terraform, git, subversion, Python, and bash/sh
OS:
Linux (Novell SuSE, Red Hat, CentOS, Amazon Linux, Fedora, Debian, Ubuntu), Unix, OSX, and FreeBSD
SAN:
AoE, EMC, and iSCSI
DB:
PostgreSQL, MySQL, Oracle, InfluxDB, Elastisearch, Couchbase, and MongoDB
Caching:
Memcache and Redis