exsp24 is not standalone. I think Native Instruments Kontakt is standalone, it's a soft-sampler too, but i don't really like it. Try it for yourself.
But if you're on a pc you can use simple hosts like Chainer or Forte to run any vsti (or even effects) standalone.
Chainer has a really good free demo version, it won't save presets, but you don't really need that anyway.
http://www.xlutop.com/html/chainer.html
http://www.brainspawn.com/
http://www.native-instruments.com/index.php?kontakt_us