When it comes to free apps on the Android Marketplace, I don't think we'll ever run out. Searching the "Just In" category almost always turns up some real gems.

Here at MUO, there's no shortage of suggestions and reviews of awesome free Android apps, like Androidify or Sorami. Then there are others like Hipstamatic that Angela covered.

No matter what you need to do, what information you need to find, or where you need to go, the odds are good that there's an Android out there that will pretty much get the job done.

5 Interesting Free Android Apps You May Not Know About

In the constant quest to offer you some new and interesting apps that you've never heard of before, I decided to take a stroll through the "Just In" pile of apps and see if there were any unique or interesting ones that caught my eye. The following five apps interested me because, at least in my opinion, they are quite useful - though so far they've been hidden in obscurity.

Display Your Own Sign With LEDr

One app that appears fairly simple, but is actually pretty useful, is the LED sign app called LEDr. The app is pretty easy to use - you just type in the message that you want to display, the lighting style, and the light color - red, blue, green, yellow, purple or white. You can even choose multi-colored lights!

The types are LED and square. Now, the LED sign scrolling across your Android screen looks pretty cool from. However, close-up it can look a little fuzzy. The square layout on the other hand, actually fills squares in a grid on the screen, rather than little, simulated LED bulbs, making for a well-defined message from up close. The scrolling motion distorted the snapshot below a little bit.

If you're creative, you could really put this little scrolling LED sign to good use. Put it up near your office computer when you have to run off for a little bit, with a message for your co-workers. Or leave it on the counter with a scrolling message on it for your kids to read when they get home from school. Be creative!

Plug Into LinkedIn With Droidin'

Another really cool app that has not received its fair share of notoriety yet, is Droidin'. Given, that's probably because not everyone has discovered it yet, but when Facebook and Twitter mobile apps are so wildly popular, I have to suspect that a mobile LinkedIn app will be just as popular.

Just about all of the core LinkedIn components are included, including posting updates, searching jobs, checking your inbox, or browsing and managing your groups.

Figure Out Your Sleep Patterns With Sleepmeter

Now, if you're anything like me - a workaholic - then you probably also don't get a whole lot of sleep. This isn't anything to brag about - lack of sleep can really hurt your health after a while. So, if you're really not sure how much sleep your getting or what quality of sleep it is, you may want to give Sleepmeter a try.

With Sleepmeter, you basically keep a running diary of how much sleep you had, as well as the quality of the sleep, including whether you had any dreams and what type of dreams you had.

All of your sleep history is logged, and you can view it under "History" and "Statistics", but by far the coolest feature is the "Graphs" tab, where you can see a running graph that shows you just how much sleep you've been getting each week.

Having such a chart and a daily log lets you identify any patterns that you may be able to fix with just a small lifestyle change.

Exercise in Repetitions With HIIT Timer

Another category of Android apps that's really popular is exercise and fitness. There are countless apps out there in the genre. However, when it comes to the specific exercises that help the most - doing repetitions for a certain period of time - there aren't many apps that are specialized enough to handle that.

A HIIT Timer actually lets you build an entire routine of exercises, with the number of repetitions and the amount of time for each set, and it'll actually coach you through the entire routine.

During the session, the screen offers a big display of the time remaining per rep, the number of reps, the exercise you should be doing during this round, and of course the overall remaining time at the bottom.

Erase Your History and Stay Out of Trouble

The final app that I wanted to cover is one of those things that you just don't think about until you get yourself in trouble.  One great way to protect yourself from any sort of your mobile phone activity getting out there is quite simple - delete it. An awesome app simply called History Eraser offers to clear every area in your Android phone that stores a log or history of your activities.

It'll wipe out your Internet history and cache, your call logs, your text message logs, and more. You can even configure the program to auto-start when you boot your phone, and you can have it automatically clear everything each time you turn the screen off. This ensures that even if someone grabs your Android and starts searching through it, there won't be anything left for them to find.

So, the next time you're bored, why not take a stroll through the "Just In" section of the Android Marketplace, and see if there are any particularly unique or interesting that strike your fancy?

Do you like any of the free Android apps listed above? Do you know of any other cool apps that most people probably never heard of? Share your thoughts in the comments section below.