Best investment?

Which would be the best investments:

SSgA PAR Fund
SSgA LB Bond Index Fund
MetWest Total Return Fund
SSgA Conservative Fund
SSgA Moderate Fund
SSgA Aggressive Fund
SSgA S&P 500 Index Fund
Dodge & Cox Stock Fund
Prudential Jennison Equity
Legg Mason
Artisan Mid Cap Fund
SSgA Russell 2000 Index
Wells Fargo Advtg Small Cap
Aim Small Cap Growth
Morgan Stanley International

Sometimes its hard to compare funds when you don't get a proper " symbol" from the plan provider...and also no one knows how old you are... ( makes a big diff)...but I'll just assume that you are youngish...and this is your first time into a 401 plan ( and you're bewildered by all this stuff that is new to you !! )
Some of the funds on your list are " Closed to new investors"...but if you can get in through some deal State Street has with them.... get into Dodge & Cox.... and AIM Small cap.... and then definitely get into Morgan Stanley international ( where most money is going to be made for a few years)
Generally I would say go with about 40% into something " moderate" Then 20- 20 - 20 into international, small or mid-cap, and SSgA Aggressive
After you are in this for awhile you will get " quarterly reports" from the plan... talk to someone at work...see if they are doing better or worse... get some info pamphlets from the plan...just get a good idea of what's going on...and learn how to move the funds on-line...
You want most of your money to be making more than say 8%...and you want the aggressive and international to be heading toward 20%.....
Within about four/five years you'll be "doubling" get a little more conservative.... work with " their " money... make it a point to NEVER accept losses without doing something about it...move, get into WHATEVER is still profitable!
The biggest mistake people make is just letting their funds " sit there"...figuring it'll all work out in the end..... knowing what's going on and doing little things about it can make the difference between a $ 200,000 nest egg and something over a MILLION.

How long do you want to invest?

The answer to this question really depends on your risk tolerance, as well as the contents of the rest of your portfolio. Morningstar.com is a great free resource on mutual fund information. Make sure to research the fund fees and expenses, as the various share classes have different fee structures that can legally be up to 8.5%, though most are not that high. Depending on your time horizon and the amount of money to invest, you may want to change your choice of share class, or put it in all one fund family in order to qualify for breakpoints in the fund expenses. If this is a self-directed account (I.E not a 401-k), you may be able to work with a financial advisor _for free_ in order to help you make the most of your choices. Advisors are generally compensated by the fees that are built-in to the funds. Hope this helps!

Only you can really answer that since only you know your criteria.

You might try Morningstar.com for their ratings of funds. A rating of 5 stars is the best. It's a free service.

get morningstar and pick a couple that have 4 or 5 stars