ORACLE CORP.

  • In 2012, the business-software giant followed up its landmark acquisition of PeopleSoft Inc. in 2005 by gobbling up Taleo Corp. for $1.9 billion.
  • Taleo itself had been a consolidator of smaller fish, having acquired Learn.com Inc., Vurv Technology Inc. and Worldwide Compensation Inc. The Taleo deal provides a stronger cloud presence for Oracle, which had long focused on software delivered "on premises."

IBM CORP.

  • Big Blue entered the HR software arena with a splash in 2012 with its planned acquisition of Kenexa Corp. and immediately became the biggest fish in the sea. Biggest, that is, in terms of market capitalization and employees (some 430,000 worldwide). IBM's market share and scope of products in HR software, though, is limited.
  • Kenexa has focused on recruiting and other talent management applications. Kenexa's acquisition of Salary.com Inc., for example, gave it compensation management capabilities.

INFOR

  • Bankrolled by private equity investor Golden Gate Capital, Infor has emerged as a serious HR software player in recent years. Building on its 2007 acquisition of scheduling software firm Workbrain Corp. for $227 million, Infor added Lawson Software Inc. to the fold in 2011 in a deal valued at $1.8 billion.
  • Lawson, for its part, had recently bolstered its on-premises HR software with a new set of cloud-based HR tools. And in 2010, Lawson had swallowed Enwisen Inc., which makes employee-communication software.

SAP

  • SAP's core HR software is used by many big firms, but SAP struggled in the shift from on-premise installations to its current cloud preference. Its $3.4 billion acquisition of SuccessFactors Inc. in 2012 could change that.
  • SuccessFactors was one of the most prominent cloud-based talent management vendors. And it had just swallowed a host of smaller firms, including Plateau Systems, CubeTree, analytics provider Inform, Jambok and Jobs2web.

CERIDIAN CORP.

  • Better known for its HR outsourcing offerings, Ceridian entered the conversation as an HR applications provider with its acquisition of cloud-software firm Dayforce Corp. earlier this year.
  • Dayforce offers core HR software as well as "workforce management" tools such as time-and-attendance, labor budgeting and weekly scheduling. Ceridian pledges to add compensation and performance management software next year.

AUTOMATIC DATA PROCESSING INC.

  • The "payroll company" is stepping out from the back office, thanks in part to an active acquisition strategy. ADP's software efforts have been bolstered by a number of acquisitions, including recruiting software-maker VirtualEdge Corp. in 2006 and benefits and compensation management software provider Workscape Inc. in 2010.
  • ADP has broadened its range of HR applications in recent years, punctuated by its launch last year of a combination of software and services called Vantage.

KRONOS INC.

  • Kronos has been the 800-pound tuna of time-and-attendance and other workforce management applications, and acquisitions have added to its heft. Having been taken private several years ago by investors, Kronos bolstered its capabilities earlier this year by snapping up U.K.-based Smart Computer Holdings and its Spanish affiliate.
  • Also this year, Kronos bought SaaShr.com, which specializes in workforce management tools.

PEOPLEFLUENT

  • Peoplefluent is another example of how private equity has drifted into the HR software waters. Investment firm Bedford Funding acquired talent management application vendor Authoria for $63 million in 2008, and snapped up recruiting software specialist Peopleclick for $100 million in 2010. The two firms were merged into Peopleclick Authoria, which then acquired analytics and workforce planning vendor Aquire in 2011.
  • That same year the company changed its name to Peoplefluent and later bought learning management vendor Strategia Communications and collaboration software-maker Socialtext Inc.

SABA SOFTWARE INC.

  • Saba is another player with roots in learning management that has broadened its product lineup in part through acquisitions. Saba bought Centra Software Inc. in 2005, which gave it collaboration capabilities.
  • Earlier this year, Saba snapped up organizational planning provider HumanConcepts.

CORNERSTONE ON DEMAND INC.

  • Talent management software company Cornerstone OnDemand for the most part has steered clear of the M&A game, warning that stitching together applications from different providers can lead to integration problems.
  • But earlier this year it purchased New Zealand-based Sonar6, which makes talent management tools designed for small businesses. Cornerstone says the Sonar6 product will remain independent.

SALESFORCE.COM INC.

  • Thanks to its 2012 acquisition of Rypple, Salesforce.com has jumped into the HR application pond.
  • Once focused on cloud-based "customer relationship management" tools, Salesforce.com now is offering a flavor of performance management software. Salesforce.com renamed the Rypple product Work.com and touts its social features and its connection with Chatter, Salesforce.com's collaboration tool.

SUMTOTAL SYSTEMS INC.

  • After private equity firm Vista Equity Partners purchased SumTotal Systems in 2009, the learning management specialist expanded through acquisitions. It swallowed Softscape in 2010, gaining a core HR system and talent management tools.
  • In 2011, SumTotal bought GeoLearning, a learning management software provider. Later that year, it acquired Accero Inc. and CyberShift Inc.