The Easy Option
By far and away the easiest option for adding interactivity to your site is to use scripts hosted by other sites. As with anything on the web, there are advantages and disadvantages with using these free services over hosting your own scripts.
Advantages of 3rd party scripts
- Quick and easy to set up
- Easy to use and maintain
- Takes up no space on your server
- Allows easy access to sophisticated and dedicated scripts
- No need to configure or fix the script
Disadvantages of 3rd party scripts
- Customisation options are usually limited
- Banners and adverts may be a condition for using the script
- Difficult to find a script that does everything you would like it to
- Other people can easily set up a rival service using the same script
- It is often difficult to exclude "trouble makers" from using the script you set up
If you do decide to go for the easy option, then there are plenty of hosted scripts available that can do a wide range of different things, from top site lists to guest books, message boards to form mail. A lot of good free web hosts offer a range of scripts that can be built in to your site and it may be a good idea to make use of them if they don't support custom CGI scripts on their server.
Suitability
Of course, the free-hosted scripts are only useful if you don't mind them advertising on the pages they create or you aren't too fussy about the look of the page.
Perhaps one of the biggest factors that will influence your choice of script is the nature of the site you wish to enhance with scripts. While it might be easier for you to use another site to process the orders for your business, visitors would be more reassured if they didn't have to go to another site to pay for goods or see adverts and buttons for things that weren't related to the site.
Sticking with the business site theme, is a free form to email script really appropriate? Sure, if you find one you can customise enough to hide 3rd party branding you might feel it is; but when you want to use it to share and store credit card details securely it will no doubt be severely lacking.
For this reason, it would be best to leave the remotely hosted 3rd party scripts to personal or hobby sites. Business and commercial sites, perhaps even some of the non profit organisations, that need to maintain a professional appearance may be better running their interactive site features on their own servers.
Keeping Full Control
The only way to get full control of a script and make it fully blend in with the rest of your site (including the domain on which it runs) is to host your own scripts. They do not have to be your own, many 3rd party scripts are available to host on your own server; but installing them on your own server will allow much more flexibility with regards to customisation and development of new features when you want them.