Is there a way to get more skill-points than normal?

Aside from altering the game files and modded items, there is a way to get an indefinite amount of skill-points. It is via the character switch glitch.

"The character-switch glitch

"A becomes B."

Nomenclature:
CSG, A.K.A. the max/infinite skill-points glitch and the backpack-space/storage glitch. Infinite skill-points is a misnomer; it isn't infinite, it's indefinite.

Instructions:
To do the glitch, open the Select Character menu as the host starts the game. The glitch has been performed successfully when the Select Character menu is open after characters spawn. The earliest way to tell if the glitch has been performed successfully is if the Select Character menu is seen or heard to open before the loading screen.

Co-ordination:
Without controlling two accounts at the same time, the CSG is usually done by having the host count down to starting the game and the glitcher presses Select Character as they start. OnLive voice chat has a one-second delay, Skype doesn't. Using a recording to count-down helps to keep consistent timing; think "Non, je ne regrette rien" by Édith Piaf in Inception. It is better to be early than late when pressing Select Character: Pressing too late means waiting for the game to load and then having to rehost. Pressing too early means that the game doesn’t start and the glitch can be retried in seconds. An efficient signal-code: Have readying up in the lobby mean being ready for the count-down to CSG.

Mechanism:
The character picked in-lobby gets from the character picked post-spawn the following data: name, level (not including XP), and missions data. Nothing else changes. The CSG is character-class blind and doesn’t change items, weapons proficiencies, nor the character picked post-spawn. It may be best to CSG firstly to back up character data. CSGing to a higher-level character causes levelling up which awards skill-points etc.. Signing back in may be required to trigger this. If you have too many skill-points, the counter will glitch and only a certain number of points may be assigned. To be able to assign the rest, switch to a different character menu tab or exit the menu (unconfirmed). After CSGing from level one to 69 back to one, CSGing to level 69 does not reward any more skill points and I do not know why. What happens when CSGing from a higher-level to a lower-level is that the character will deal the damage of the new, lower level, but whatever was equipped before will stay equipped even if the Level Requirement is now too high. The character levels back up to their original level, as determined by their XP, the next time that they sign in.

CSGing to have completed DLC4 ("Claptrap's New Robot Revolution") seems to award its skill-points somewhat retroactively. Playthrough two is not unlocked until the Destroyer is defeated. Even CSGing to a character with pt. 2 unlocked does not unlock it on the switchee. CSGing from level one to a 69 with mission progress in pt. 2 then CSGing back to fresh does not unlock playthrough two.

F.A.Q.:
“Okay, I’ve got the character selection menu open. What do I do now? Who do I pick?” Depends upon what is desired.
“I want more backpack space.” A character that can still do the Claptrap Rescue missions must be picked. The explanation-paragraph of what the CSG does answers your question.
“OK, I picked a new character so I can go through the game again and do the Claptrap Rescue missions.” I hope you were careful against story-blocks in your decision. Don’t forget that you might want to change your name then have it save before or as you leave.
“Hey, the character that I picked in the lobby was level 69 but I’m level one now.” The next time that that character signs in, they will level up by their XP.
“OK, I CSGed my level 69 to a new character. How do I get more backpack space?” Rescue CL4P-TPs.

Dangers:
You won't hear ECHO comms that you've heard before. This seems to result in...

Story-blockage:
If a character, who has progressed beyond story-blocks points, is CSGed back to behind any story-block point, they will be story-blocked when they re-encounter them. The story-block points are that:

• Dr. Zed never talks to you nor opens his garage gate door in Fyrestone for the “The Doctor Is In” mission,
• the Guardian Angel never talks to you to give you the “Claptrap Rescue” mission to repair the Fyrestone Claptrap who opens the front Fyrestone gate,
• killing Skags doesn’t count towards the “Skags at the Gate” mission, and
• killing bandits doesn’t count towards the “Blinding Nine-Toes” mission. The uncounting can fix itself though and I don’t know how.

Those are the story-blocks at the beginning of the game. Near the end of the game, the story-blocks are that:

• the Guardian Angel never speaks to you to open the Trash Coast teleporter, and
• Patricia Tannis never gives you the “Steele Found” mission after “Reactivate the ECHO Comms System”. Story-blocks seem to result from what I call automatic missions. Automatic missions are missions that are given to you involuntarily, often following an ECHO comm. There are no DLC story-blocks caused by CSGing.

Too many weapon slots:
By regressing to a point where a mission that awards a Weapon Equip Slot SDU is undone, completing such a mission can award Weapon Equip Slots above four. Such slots are unseen in the inventory menu. Switching to a weapon in a >4th (greater-than-fourth) slot is done by scrolling to it. Anything equipped in a >4th slot is unequipped next sign-in. There seems to be no limit to the amount of >4th slots that can be gained.

Special thanks to HolyCrap-_-Lmao who brought the glitch to OnLive."

You can earn 2 skill points in Mad Moxxie's Underdome.