LONDON -- If you want to be eligible for company dividends, you must have purchased the shares before the ex-dividend date and held onto them at least until the market opens that day. The price of shares usually falls on ex-dividend day, too, as they no longer carry that extra bit of cash.

That makes ex-dividend day important for two sets of investors -- those who want the dividend and those who look for bargains when shares fall by more than expected. Here are three going ex-dividend next week that you might want to consider.

On Feb. 20, BHP Billiton released interim results that reflected the tough year the mining sector has had. Revenue fell 14% to $32 billion, with earnings per share plunging 58% to $0.80. But that was largely expected in a year of falling mineral and metal prices. What counts for us is the company's interim dividend, which was raised 4% to $0.57 per share. The shares will go ex-dividend on March 6, and the dividend will be paid on March 28. The share price currently stands at 2,086 pence.

Bringing you two miners for the price of one, Rio Tinto (LSE:RIO) -- a Fool Beginners' Portfolio constituent priced at 3,511 pence per share -- will go ex-dividend on the same day after lifting its full-year dividend by 18% to 106.77 pence per share. The final instalment, of 60.34 pence, will be paid on April 11.

Shire (LSE:SHP)
Pharmaceuticals company Shire announced a strong set of 2012 results on Feb. 14, showing a 10% rise in total revenue to $4.7 billion. Non-GAAP diluted earnings per share came in at $6.10, up 14%. For the second half of the year, Shire will pay a dividend of 9.39 pence per share, with the ex-dividend date set for March 6.

The payment, which will be made on April 9, takes Shire's total dividend to 11.13 pence per share for a yield of 0.5% on the current share price of 2,100 pence.

TUI Travel (LSE:TT)
On Dec. 4, travel operator TUI Travel announced a final dividend of 8.3 pence per share, lifting the full-year payout by 4% to 11.7 pence per share. On a share price of 310 pence, that's a yield of 3.8%. It will not be paid until April 9, with the ex-dividend date again being March 6.

TUI has managed to keep its dividends growing throughout the recession, and there are further rises forecast for this year and next, which should be well covered.

Dividends like these can add nicely to your investment returns -- they can be spent or reinvested, according to your needs. Whether you're investing for income or growth, good old cash is always welcome. And that's why I recommend the brand-new Fool report "The Motley Fool's Top Income Share For 2013," in which our top analysts identify a share they believe will provide handsome dividend income for years to come. But it will only be available for a limited period, so click here to get your copy today.

Alan does not own any shares mentioned in this article. The Motley Fool has a disclosure policy. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. Try any of our Foolish newsletter services free for 30 days.