In addition to using sources familiar to you (textbooks, WSJ, etc.), consider browsing other resources for ideas about recent trends in accounting and taxation (and related fields, including finance and economics).
The Big Four:
Journal of Accountancy
AICPA Tax Reform Resource Center -- "Here you will learn what Congress is proposing and what has passed, find analysis from our tax experts, read about our advocacy efforts, and access guidance and tools to help you understand and apply the changes. We are exploring reforms' effects on firms, employers, clients, small businesses and individuals and will update the site regularly."
AICPA Insights -- the official blog for the American Institute of CPAs. This overview of timely issues affecting the accounting profession may generate ideas for your research topic.
Accounting Today -- mostly news and practice-related articles, but these may spark an idea about a possible research topic:
Knowledge@Wharton / Perspectives@SMU / HBS Working Knowledge:
NYU Stern School: Accounting Department [Research] / Ross Institute:
University of Chicago: Accounting Research Center -- research papers
CFO.com -- Accounting & Tax, includes daily articles and updates (and lots of ads) of potential interest to financial executives. Some stories may inspire research topics.
Are you smarter than a 1917 CPA? See if you can answers these questions from the 1917 CPA exam.
RIA - Checkpoint -- includes the RIA U.S. Tax Reporter; Citator; public domain cases; tax advisors planning system; practical tax strategies; and articles from the Journal of Taxation and Journal of Corporate Taxation.