DesignaKnit 7
Not compatible with Windows 7. They have a new version coming out in September which I've emailed to find out about. Looks like it does chart and garment design for hand and machine knitters.
Price - Oh look $199 (£127) for handknit only version.
EnvisioKnit
Very slick chart software. If you are trying to create a pattern where you already know the pattern for the item you're going to apply the chart to - say a mitten or sock or even a whole fairisle jumper - then this allows you to create multiple charts using colours and stitches. I especially liked the colour picker which showed you the complimentary/triad/any other type of colour thing matches for the one you had chosen. Fully Windows 7 and Mac compatible, it exports in every format you can think of including pdt, pdf and docx. Nice demo version too.
Downside - cost
Upside - very nice interface. This is the one you would put on your xmas list or save up for.
Price - $99 (approx £63)
Intwined
Attractive chart making software. Useful tools to help create repeating charts, mirrored effects, add colour etc. Extensive stitch library (200 including cables) which you can also modify or add to. Can export to PDF or as an image file and can copy and paste the text. Updates the text as you alter the chart and vice versa. Good demo video on their site and extensive userguide. Available for Macs and Windows.
Downside - no demo you can download to try out (although demo video very good)
Upside - Looks like you get software updates for free.
Price - $44 (approx £28)
KnitBird
More chart making but definitely aimed at the hobby crafter and quite a cutesy interface that will probably distract you from the lack of features - although it is still good for the price. With this you purely get a chart without the written instructions. One thing I haven't seen elsewhere is the ability to add text (in arial or times) and import images into your charts. The image importer is nice as it allows you to adjust the level of pixelation/detail and hence the size of the chart.
Downside - basic software but fine if that's all you need.
Upside - intuitive and attractive with text and photo import options
Price - $30 (approx £19)
Knit Visualizer
Looks like a chart generator. Price put me off looking for more details.
Price: $185 (approx £118)
KnitWare Basics/Sweaters/Skirts&Shawls
Tell it your gauge, type of item you want to knit, machine knit or crochet and adjust to your measurements. It produces a pattern for in the round or flat assembly. Don't like the neckline? Change to another. Want raglan instead of saddle shoulders? Click and it's done. Have a repeating stitch motif? Tell it the repeat length and it adjusts the pattern so the repeat is centred on flat bits or fits onto an in-the-round garment. This was my first choice system UNTIL I came to check the compatibility with my laptop. I had tried the demo on a borrowed one and really liked the interface and the option of different systems for basics, jumpers and shawls. Plus they were only about £20 each so for less money I got more variety of garments. And then disaster struck. If you have Windows 7 64-bit then you have to blah blah.... So gutted.
Downside - doesn't work on my machine without a load of fannying about which I can't be bothered with.
Upside - All sorts of patterns can be created and adjusted as needed.
Price - £20 per program (approx $32)
Here is a cat picture to break up the text.
Sweater Designer 1.5
Doesn't work on my machine. Is Windows 7 really so outrageously advanced that compatibility is impossible to achieve? 80+ motifs to use on 6 sweater styles. $1 plus postage for updates.
Price - $49 (£31)
Sweater Wizard 3.0
Want to knit a jumper or cardigan flat or in the round? Kapow. Very like KnitWare but will actually work on my machine (always a bonus). Allows you to use various techniques like steeks or three needle bind offs. As well as collar shapes it also has 'collar trims' which means cowls, hoods and turtle necks. Overall this one is pretty sweet and the support looks to be pretty good with both a Ravelry and a Yahoo Group.
Downside - you have to pay for upgrades. $28 too which isn't pin money.
Upside - Basically does what you want.
Price - Official website quotes $90 (approx £57) but available for $68 (£43) elsewhere. Or $58 (£37).
StitchMastery Knitting Chart Editor
Very similar to Intwined but with a more sophisticated menu system which could make it quicker to use in the long run. It also comes in a Linux version as well as Mac and PC which might set the hearts of geekier knitters racing (the Linux version is even 10% cheaper than the others). Unlike Intwined this does have a demo version you can download which might make you more confident in buying, especially considering the price.
Downside - purely the financial. That much money for something that only does charts?
Upside - Software updates included and lovely menus.
Price - £60 (approx $95)
If I missed the software you like let me know in the Comments below.