For Constructing
Crossword Compiler (for Windows) by Antony Lewis
Crossword Compiler is considered by most constructors to be one of the best puzzle-making software package available. Very feature-rich. The developer regularly consults with puzzle constructors with regard to desired features and functionality.
Crossfire (for multiple platforms) by Robert Stockton
CrossFire is an innovative new tool for creating professional quality crossword puzzles. It has been designed from the ground up to provide all the power you need, without any added complexity to get between you and your creative muse. Whether you are a crossword pro looking for a new tool to simplify your workflow, or a new convert who is ready to learn just how simple and exciting it can be to create new puzzles, CrossFire will give you the tools that you need to take your puzzles from concept to completion. Best of all, you won't have to shop for a new machine or install Parallels: CrossFire gives you the same puzzle-building power no matter what your computing platform.
CROSSDOWN for Windows by Sam Bellotto Jr.
Bringing all the challenge and enjoyment of solving and constructing real crossword, acrostic and now cryptogram puzzles exactly like the ones found in the daily or Sunday newspapers to any Microsoft Windows environment! Crossdown software has been praised by professional puzzle constructors and avid solvers around the world for its intuitive interface, powerful features and pure fun content.
Cruciverbalist for Mac
I don't use a Mac but I have heard nothing but good things about this program. Apparently the package to get if you're a Mac user.
Alex Boisvert's crossword tools
Alex has put together a bunch of useful tools for constructors and solvers. Check it out!
For Online Solving
Across Lite software by Litsoft
-- Two thumbs way up. All online puzzles should be offered in Across Lite.
crossword player for Mac OS X. Black INk is based on MacXword, the original Across Lite crossword client for Mac OS X. It has a new name and new features. Check out the details on the website!