according to my calculations exact lengths are, Left: 261.4, Right: 260.3. Rounded would be L: 261, R: 260. And you could use 261mm spokes for both sides with no problems. This is assuming a 26" Crest 32 spoke laced 3 cross. Since you didn't include this information in your post it must be assumed.
That is assuming that you trust my calculations. I will never take anyones word for it when it comes to spoke lenghts. I much prefer to do my own. Then there is no one to blame if they aren't right but me!
I would suggest downloading one of the avaivable spoke length calculators and doing it yourself, or you could go to Roger Musson's website and use his online calculator, http://www.wheelpro.co.uk/spokecalc/
You'll need the measurements for the hub and the ERD for the rim. Both of which are available on their respective manufacturers website. The measurements you'll need are the distance from the Center to the Left Flange of the hub, Center to Right Flange, the Left Flange Diameter and the right Flange Diameter for the hub. For the Rim you'll need the Effective Rim Diameter or ERD. All in milimeters of course.
I would also suggest learning to measure hubs and rims yourself. Instructions for measuring your hub and rim can be found here, http://www.sheldonbrown.com/rinard/spocalc.htm
. There is also a downloadable Excell spoke calculator available. I use a version of it and have found it to be quite accurate.
Since the DT Swiss caclulator no longer includes a data base of hubs and rims other than DT's own products, it would be a good thing to learn to do it yourself. It's not difficult and can save a world of headache should you not be able to find rim or hub dimensions on a manufacturers site. Or the manufacturers dimensions are known to be untrustworthy, which does happen more than you think for.