Good sites and great suggestions especially in the second link. Give them a try. But always stay under the limit and don't go beyond such that you end up breaking your precious fingers.
For practicing on the guitar I would suggest following finger exercises (while playing):
Using fingers 1 and 2:
$6 1 3 $5 1 3 $4 1 3 $3 1 3 $2 1 3 $1 1 3
and back up. Make sure your 1st finger is in the 1st fret when you play the 3rd fret with your 2nd finger.
With fingers 1 and 3:
$6 1 4 $5 1 4 $4 1 4 $3 1 4 $2 1 4 $1 1 4
and back up. Make sure your 1st finger is in the 1st fret when you play the 4th fret with your 3rd finger.
With fingers 1 and 4:
$6 1 5 $5 1 5 $4 1 5 $3 1 5 $2 1 5 $1 1 5
and back up. Make sure your 1st finger is in the 1st fret when you play the 5th fret with your 4th finger.
Follow the above pattern (by playing a fret higher than your comfort zone/fret) for EVERY PAIR OF FINGERS (except 2nd and 3rd fingers as it can become quite uncomfortable playing this pair, but you can always give it try and it might work well with you).
This can be a great exercise for finger stretching and can help you in the long run either for chords or soloing.
PS: (If you have learned hammer-on and pull-off, the above exercises can be used for them too)