BOSTON ( TheStreet) -- The S&P 500 has risen 5.6% so far in 2010, underperforming bonds and trailing last year's stock-market performance. Still, some companies have produced outsized gains. Here is a look at the 10 best-performing S&P 500 stocks of 2010 and their prospects for next year. They are ordered by year-to-date return, from big to biggest.

10. Citrix Systems ( CTXS) is a Fort Lauderdale, Florida-based software-as-a-service and cloud-computing company, designing programs that allow individuals to access data regardless of location, device or network. Citrix's top product, XenDesktop, enables employees to work on a virtualized desktop through company-owned laptops and their home computers. Other products include GoToMeeting, XenServer and NetScaler, which aims to reduce infrastructure costs and boost program speed. Citrix acquired VMLogic during the third quarter. It invested in Kaviza and bought Paglo earlier in the year. An acquisition strategy and strong demand for cloud-computing helped boost sales 66% in the past 12 months and earnings per share 61%.

Outlook: Citrix's stock has delivered outstanding gains in 2010, jumping 61%, but analysts have moderated their views. Of those covering Citrix, 12 advise purchasing its shares, 20 recommend holding and one suggests selling them. A median price target of $63.06 implies that the stock is 5% above fair value and will decline in the next 12 months. Bullish forecaster Lazard Capital Markets expects the stock to advance 21% to $80. On the other end of the spectrum, JPMorgan predicts the stock will drop 32% to $45.

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