Thought i'd share this great DIY DJ idea from the web....read on...(my comments and Avg cost in brackets)

"How to DJ Your Own Wedding With an iPod or Laptop
DIY DJ Tips and Tricks

By Nina Callaway, About.com Guide

DJing your own wedding is a great way to save money and it allows you control of your reception playlist. Yet a DJ does a lot more than just push play, and if you don't plan ahead, you might end up with poor sound, the wrong songs, or technical difficulties!
What You'll Need to DIY DJ Your Wedding

Obviously, you'll need a reliable Mp3 player such as an IPod/Mp3 player/Computer capable of holding enough music (Enough music is about 150 songs...or 25 songs per hour, cost about 1.20 per track $200.00). I recommend that you have a playlist that is an hour or two longer than the length of your reception, which will allow you to start the music before guests arrive and have backup. You'll also need a good speaker system, a mixing console, a microphone (either wireless or with a long enough cable), and a cable to connect the Mp3 player – most likely a mini-stereo to dual RCA (male) cord, depending on your mixing console. (Average cost for a PA system rental like this $500.00)

Test It Out!

This might seem obvious, but you'll want to leave plenty of time to test out your system and speakers. (Time for set up about 1.5 hours) You may need a different kind of cable, or your mp3 player might not play well with others. (Whoops...better find that cord in sound check mode) Rental equipment has been known to fail, (TRUE) and you'll need time to get a replacement delivered. (Time? to get 2nd system up? about 1 hour...maybe) Static, feedback, poor sound balance, and low volume are just a few of the problems you might encounter. If your venue does weddings regularly, chances are they can walk you through the DIY DJ setup, but it's better to be safe than sorry. (cost for this... 75.00 to 100.00 for system delivery, $250.00 for a tech to deliver run and remove the system at the end of the night...totally worth a TECH!!!!! Trust me!)

Have a Backup Plan and a Backup Backup Plan

Along with your main Mp3 player/Computer and its power cable, it's a good idea to bring a second Mp3 player or a laptop - all loaded with your music. You'll also want to have on hand the name of an equipment rental company who does last minute deliveries. In case no one is dancing and you need to switch directions, you'll want that extra hour or two of music mentioned above. Odds are, you won't need any of your backups, but the cliché of "it's better to be safe than sorry" is especially true in this case.
Prevent "Guest DJs"

There's always that one guest who doesn't like what's playing and tries to change things up. Instead of bombarding a regular DJ with requests, she'll be trying to hit shuffle on your playlist, or even switch the cable to her own device. But you can prepare for this bad wedding guest. First, ask for music requests, either on your wedding website, or on your reply cardswith a line like "Name some artists or songs you're hoping to hear at our reception" or "What songs are sure to get you dancing?" Hearing a favorite song might satisfy a would-be guest DJ, but in case it doesn't, you should have an IPod minder or "freejay" who can guard and hit play for any special songs. When the freejay inevitably needs to take a break, hide your device under a taped-down piece of paper that says, "We've chosen our wedding playlist carefully. Please don't touch the IPod!"
Make a Music Plan and Checklist

Make sure you've got a song for every special moment in your wedding, from the first dance to the last one. Here's a wedding reception music plan, which will make sure you know which song should be played and when. Load these key pieces of music onto a separate playlist, ready to cue when necessary, or use an app like MyWeddingDJ.
Crossfade and Cut

One of the most important things that a DJ does is create transitions between songs. Six seconds of silence might not sound like much, but it's certainly enough to kill a mood and empty a dance floor. You might also have a favorite tune with a long intro or an extended ending that just won't work. Fortunately, there are DIY DJ solutions to these problems. Some models of IPod/Mp3 player/Computer allow gapless playback. You can also use iTunes to both crossfade and cut songs, and DJ apps like Virtual DJ can help you with advanced techniques.

Amplify It

Music that sounds plenty loud in an empty room will be a mere whisper when it competes with a hundred people chatting and laughing. Even if they are completely silent, their bodies alone will absorb sound. Your space may already have a speaker set-up, but be sure to test it out. Many have older speakers that don't operate well at loud (dance level) volumes, or which may need to be supplemented with additional woofers and speakers. You can rent a basic set-up of an amp and some speakers for about $100 in many areas of the US. (not true here in Central Oregon)

Play Crowd Pleasers and Music That Will Get Them Dancing

As soon as I posted my Do Not Play List, I started to hear complaints from professional DJs that these were the best songs to fill a dance floor. While I agree that you can use the Chicken Dance or the Electric Slide to bring out some shy folks, there are better and less cheesy ways: Wedding Music To Get Guests Dancing. One of the prime reasons to DIY DJ is that you can control what gets played and avoid the cheese, but I think we can all agree that your wedding is not a time to play only death metal or emo music. You need to think about your guests as well as yourselves.

Don't Rely on an Internet Connection

Streaming music services like Spotify or MOG are great for personal listening, but they can cause big problems at a wedding. If the internet connection goes out or resets, you'll be left without music. Instead, use offline music sources. (like your MP3's, ipod, ipad or a Laptop with loaded music and playlists..)

Reconsider Hiring a Professional DJ
(I like this part)

So all these tips might leave you feeling more prepared. But they could also be overwhelming -- suddenly the simple DIY DJ isn't as simple as you thought. Once you add up the cost of of renting equipment, system delivery...set up take down, and purchasing songs, and the time you'll spend making playlists and getting prepared, you may decide that it's worth it to go pro. To save money, you could consider using a DIY setup for the cocktail hour, and a pro for the reception. (many DJ's include an hour or more of music for dinner & cocktails)

So...if you were doing the math...a DIY DJ can cost you a mere $850.00 plus! Where is the savings in a DIY DJ?