Hi Pat,
I'm not aware of anywhere that tracks companies that are undergoing share buy-backs, but I'd sound a note of caution about it being a good indicator for the company. Often the market will mark up a company's shares for a buyback programme, but this is usually in the latter stages of a long bull market where the market is nervous about the company splurging cash on acquisitions, and would rather see it handed safely back to shareholders via a buyback or special dividend. Also the mark-up will occur instantaneously when the company announces the buyback, or even before, in anticipation, so it's difficult for a private investor to be ahead of the market in taking advantage (the share price uplift from a buyback is a simple calculation, and the market should discount it immediately). But the negative view is that the company should be investing in growth (either organically or through careful acquisition) and if all it can think of doing is giving excess cashflow back to shareholders rather than re-investing, it can demonstrate a lack of growth options (or imagination) for the company. Ultimately, no value is created through a buy-back, and it can be done for cynical reasons (eg enhancing eps, if that's a performance metric for director bonuses).
Personally a better indicator I think is director buys/sells. After all, if the CEO is prepared to invest a hefty chunk of his own personal cash then that really should be a good sign. The FT, or a website like Digital Look, lists major director buying and selling activity. Personally I put less emphasis on selling unless there is more than one director doing it, as it may just be that the boss needs to put a downpayment on his new yacht, or pay off his old wife for the new trophy blonde on his arm, rather than a specific problem with the company.
Hope that helps.