The latest patch is 1.96 and you can get it from the official site.
http://www.flashpoint1985.com/download/download.html
The FDF mod is top-notch and as if a very high-quality campaign in the current day FDF weren't enough it also includes a ww2 portion!
It's a must-download if I've ever seen one.
http://www.fdfmod.org/downloads.html
If you just want to enhance the gameplay of Flashpoint itself, get the latest WGL. It won't affect the original missions and campaigns I'm afraid, but if you plan on making missions yourself or if you want to play it on missions others made for it it's a good mod to have.
http://wargames.armaholic.eu/wglhelp/index.php?page=Download
I
think this is the correct link. I know I downloaded it from a different looking page back in the days.
If you want to enhance the atmosphere of Flashpoint, download the latest ECP. It mostly changes little things and you could see it as an extensive patch for Flashpoint. It's compatible with the campaigns as far as I know. Changes include 3d craters for explosions, randomly bailing random crewmembers if armored vehicles get destroyed and radio chatter among your troops.
There is almost no reason to play Flashpoint without it unless you are a purist or you have another mod running that isn't compatible with it.
http://www.ofptf.net/fullitem.php?id=18&titlecat=addo&tsufx=addons
If you want to enhance the look of the game the latest installment of FFUR is your mod. It also changes the equipment though, so it's not just a remodeling of Flashpoint but it changes things. Check a few screens if you like it.
http://ffur.net/ofp/
The GRAA mod is very good too. It includes new models and animations and a new third person camera that looks a lot like the one in Ghost Recon 2. It has a config-file in which you can active/deactive almost all of the changes the mod makes so you can really tweak it to your liking.
I played with this for quite a while.
There is also the "winterpack", which adds winter versions of existing islands as well as winter versions of existing vehicles and units. So it's not just the ground-texture changed to white, but buildings are covered in snow, plants look frozen over, vehicles have a little snow on them, etc. If you want to make winter missions this is a great pack to have.
FDF has winter islands too, so if you have FDF you might not need this.
I can't find a good link for these two right now. Sorry. But GRAA is worth searching for.
Make sure to install Kegety's hi-res skies! They don't really conflict with anything and they look really stunning.
http://www.kegetys.net/ofp/index.php?p=others
There is also the dxdll by him which adds some special effects like Bloom, but it
really drags the performance down! For me it wasn't worth it but feel free to check it out and see if you can use it.
http://www.kegetys.net/ofp/index.php?p=others
I had a beta of a then-discontinued ww2 mod about Normandy. It had at least one great island (with grass!) and a few good infantry weapons for both the allied and the axis side. I don't remember any vehicles but I think it had some. There were no missions for it back then, but if you plan on making some yourself I'd recommend this mod.
Unfortunately I forgot the name. If someone could help out here that would be very nice. I'd like to have it again, too.
EDIT: Found it! Invasion 1944 - Oosterbeek v2.5. Download-links are in here:
http://ofp.gamepark.cz/invasion1944/public/index.php?topic=89.0
I also added links for most of the other addons/mods.