I've posted about this before but I thought it was worth posting about again. Griff, the mobile music studio for Windows mobile, is free.
So, if you have an old Windows Mobile device knocking go can grab Griff as it and all it's plug ins are now free.
If you don't have an WinMo device I can recommend a Dell Axim X51 which has always done really well for me.
Dell Axim at eBay