ok fellows, it is a bit older thread but I'm going to add a very simple solution. A very very simple file server, not with any options, but simply access required files and download if needed. I'll try to explain step by step, not an expert in writing tutorials yet.

1. install Apache 2, open terminal, type "sudo apt-get install apache2", provide password on prompt, wait for it to install, respond accordingly if install requires a response.

2. do not close terminal yet. type "gksudo nautilus", provide password on prompt, a file explorer window will open. At this point, be very very careful as all your file system is open to you with all securities removed.

3. click on "File System" in left side menu. browse to the folder which you want to share over http. FYI, your home folders will be in "/home/username". username is the your ubuntu login username.

4. right click on folder to be shared, select "Make Link" from popped menu. a link will be created at same place.

5. now, right click on that created link and select "cut" from popped menu

6. click on "File System" in left side menu again.

7. browse to folder "var" and then to folder "www".

8. right click on empty space and select "create new folder". name it whatever you want.

9. open that newly created folder and right click in empty space and select "paste". your previously made link will be pasted here.

10. now, open firefox or chrome or whatever browser you like. in address bar type "http://localhost/foldername" foldername is the folder you created in /var/www.

That's it you are done, you'll see the name of folder you actually wanted to share in a list opened in front of you in your browser. click it and all your required files/folders are right there. click on any file and it'll be downloaded/opened accordingly.

I hope instructions are clear and helpful.