Well kitten, there are a lotta options out there, and very few explain in plain English what they do and don’t offer, or how they might actually be of use. Plus, most of them are written for pure geeks, since that’s who generally implements them. As your translator and guide, I’m going to help you narrow it down from the point of what you need, versus what’s being sold.

MINIMAL
If what you need is a clean, simple slideshow for a half a dozen shots (e.g. to add some ambience/fun to a page), then what you want to ask for is a “basic slideshow with automatic transitions, no captions, no controls.” Something like this or this (scroll down) or this.

STANDARD
If what you want is a larger gallery of images, with thumbnails, captions, user-navigation controls, then what you want to ask for is “a gallery slideshow with customizable captions, transitions, and user-nav controls.” Something like this, or this, or this (which is similar to iTunes CoverFlow). Or even a super-sized version, like this.

DELUXE
If you have multiple categories of images (e.g. photos separated into “interiors” “exteriors” “annoying in-laws”) etc then you need to add “multiple galleries” to the description. As with cars, more options = higher price. At this point, you’re probably looking at a Flash option.

Thumbnails: don’t settle for a row of numbers. Tiny preview versions of each image make navigation much more intuitive and efficient. This is an automatic process with most plug-ins, so the cost difference is minimal.

WHICH FORMAT?
Most options boil down to 2 choices: Flash or jQuery. Both are fully compatible with most modern browsers. They can both be customized to match the look and feel of your brand. While some search engines do not scan the text captions in either option well, fret not, as there are legitimate workarounds. Both can be embedded in your page alongside scannable text and other navigation (i.e. your site does not have to be all Flash, and yes, you can have permalink pages with flash embedded for easier sharing and bookmarking). Both can display video. Here’s where they differ:

FLASH (with XML)
Pros:
1) More features for animation, games, or video.
2) Better quality results for video using .flv format.
3) Audio (sound/music options) is more developed in flash.
4) Plug-in is free to download in the unlikely event that a user has an ancient browser (circa 2001).
5) All images display in a uniform size = formal, consistent presentation.
6) Considered more deluxe (more features) and more robust as it’s been around longer than jQuery.

Cons:
1) Does not display on iPhones (yet).
2) Old versions of flash slideshows use a client side plugin = possible slower downloads (translation: your user’s computer must do the heavy work, so mileage may vary, depending on age/speed of each user’s computer). Be sure to ask for Flash + XML/actionscript to avoid this.
3) All images must be the same width/height ratio to avoid distortion. Yes, the images can be auto-processed to achieve this with mixed results. If you’re big on quality, don’t skimp on this, have the images processed manually in Photoshop.
4) Can be more expensive as it requires a Flash programmer to create the initial file.

jQuery
Pros: the current darling of developers, it has fewer features than Flash, and is therefore simpler to code. It’s perfect for basic slideshows and galleries.

1) Displays on iPhones and other mobile smart phones. Yay!
2) Overlay effect (page dims in background, image gallery floats above it) = users less likely to leave your site or get lost. Great for large sized images.
3) Images can vary in width/height = less prep time for each image = cheaper maintenance.
4) Server-side includes = fast downloads (translation: all the heavy lifting is done by the website server, not your user’s computer)
5) No download necessary. Ever.

Cons:
1) Fewer features than flash.
2) Images display at different height/width sizes = less formal, less cohesive visuals. While this might be a plus for some brands, if you’re aiming for a high-end market, casual is generally not advised.

So. Do you need a deluxe version or a basic?

Imagine a corner of the coffee lounge converted (as needed) to a “Give us 5 minutes, get a free latte” space. One at a time, marketers could set up a simple trade-show booth display and conduct sample testing/focus groups/surveys with willing volunteers that fit their demographic. Five minutes in exchange for a $5 coffee. Hey, if you’re in there anyway, and you’ve got 5 minutes to spare, why not?

LOGISTICS
Sure, the store could use a simple drink ticket system: the marketer hands the consumer a ticket after they’ve participated, which the consumer then exchanges for a coffee, and the barista later tallies for a bill that the marketer pays at the end of their session. This would keep it simple and flexible (time-wise).  But better yet, a sticker like the kind used for admission at museums, marked on the back with the date and marketer’s signature, that says something like “I scored a free latte at ______(insert name of store)”  would further promote the store, while also advertising the wearer’s resourcefulness to friends and colleagues.  The store’s website could offer an instant alert via RSS feature for volunteers depending on what demographics they register under (“Free latte alert: Rosie’s Cookies and Cakes is holding a taste-testing and survey at our Main Street store from noon to 1pm.”)

COST
Assuming each volunteer cost the marketer the most expensive drink in the house, it’s still a lot cheaper than the $20 – $50 an hour that they pay individuals to attend focus groups, not to mention a lot easier to organize and manage.

WIN-WIN-WIN
It’s a win-win-win: free lattes during hard times; increased foot traffic to the stores, not to mention free press and lots of word-of-mouth; and an easy way for entrepreneurs and small businesses to test their products and services on remarkably willing test-subjects.

JUST SAY NO
How do you say No to willing participants that don’t fit the demographic? Easy: a pre-registration form (online, which can be accessed at any in-store terminal) where they declare their various consumer preferences and categories. This is automatically matched to whatever the marketer has checked off and the result is either “Yes, come on down!” Or “Sorry, we have no matches for you today. Please try again soon.”

Somebody please take this idea and use it. I want a free latte, dammit.