Welcome to the Forums. A bit more data in the bio will normally help get a more appropriate response.
From the tenure of your post, I am assuming that you have no other form of electronic cartography. Use of the laptop for your main nav station will demand a fair bit of power and must be included in your energy budget. Personnally I prefer having a plotter for the short term navigation, and the laptop for the passage planning.
In order to decide what software you need, you really need to decide beforehand what sort of cartography you want. A lot of the cheaper systems use raster charts (paper chart scanned in). I much prefer the Vector systems and C-Map is my system of choice. C-Map has by far the most up-to-date cartography (can even get email updates). It also has two systems that make it superb for the long distance sailor:
You can exchange a plotter chip for a different area for the same price as an update to the original area. Email for the new chip to be delivered at a forwarding address, and you then have another 30 days to return the old one.
Once you have the plotter chip, you can either use this chip in your laptop via a dongle, or pay a much reduced price for a CD of the same area.
Assuming you are still interested in the C-Map option, IMHO the best software to utilise this is <A target="_blank" HREF=http://www.chartwork.com/html/winchart_nexus.html>Winchart</A>, and this also provides a weather routing option.
I have no connection with either company, but have researched this at length for my own long distance plans
I use Maxsea and have the weather routing and performance options. Personally I find it excellent. It does all of the donkey work and you can recalculate everything in realtime. Additionallly they have a weather email sevice where you can get free weather forecasts for the next few days. This is in compressed form which is good if you are downloading via an expensive sat link.
It does calculate tidal routes although there was a software glitch one or two versions ago. What it does is to first look at the expected boat speed obtained either from manually entry or from user entered polars. It then calculates optimal routes and it is possible to move time forward to see the expected boat position and direction of tidal flows etc throughout the passage. One caution though is that I think one needs the routing module and it is necessary to buy the tidal stream data separately. It would therefore be sensible to add up in advance the total cost of the package you want.
Mariner Computers used to do a CDROM with all the demos on for you to try. it might be worth a email to see if they still have any.
<A target="_blank" HREF=http://www.marinercomputers.co.uk>http://www.marinercomputers.co.uk</A>