American Capital Strategies - This publicly-traded buyout fund has a site rich in articles and tools that explain the mezzanine, subordinated debt and private equity markets.
MoneyHunt - Online version of the TV program MoneyHunt
Next Wave Stocks - Bills itself as a site on stocks of the "new economy," but actually even more comprehensive than its name suggests,
including links to venture capital firms and angel investor sites, M&A database and initial public offering highlights.